Merge pull request #2994 from vitorpamplona/claude/nip52-calendar-screens-yQc3j

Add NIP-52 calendar events support with UI and reminder system

amethyst/src/main/java/com/vitorpamplona/amethyst/AppModules.kt

@@ -721,6 +721,12 @@ class AppModules(
         ScheduledPostWorker.schedule(appContext)
         ScheduledPostWorker.scheduleCatchUp(appContext)
 
+        // Periodic scan that posts "starting soon" notifications for NIP-52 appointments the
+        // user has RSVP'd to as ACCEPTED. 15-minute cadence matches both the WorkManager
+        // periodic minimum and the lead-time window.
+        com.vitorpamplona.amethyst.service.calendar.CalendarReminderWorker
+            .schedule(appContext)
+
         // Watch for account login and start/stop always-on notification service
         applicationIOScope.launch {
             sessionManager.accountContent.collectLatest { state ->

amethyst/src/main/java/com/vitorpamplona/amethyst/LocalPreferences.kt

@@ -104,6 +104,7 @@ private object PrefKeys {
     const val DEFAULT_DISCOVERY_FOLLOW_LIST = "defaultDiscoveryFollowList"
     const val DEFAULT_POLLS_FOLLOW_LIST = "defaultPollsFollowList"
     const val DEFAULT_PICTURES_FOLLOW_LIST = "defaultPicturesFollowList"
+    const val DEFAULT_CALENDARS_FOLLOW_LIST = "defaultCalendarsFollowList"
     const val DEFAULT_PRODUCTS_FOLLOW_LIST = "defaultProductsFollowList"
     const val DEFAULT_SHORTS_FOLLOW_LIST = "defaultShortsFollowList"
     const val DEFAULT_PUBLIC_CHATS_FOLLOW_LIST = "defaultPublicChatsFollowList"
@@ -361,6 +362,7 @@ object LocalPreferences {
 
                     putString(PrefKeys.DEFAULT_POLLS_FOLLOW_LIST, JsonMapper.toJson(settings.defaultPollsFollowList.value))
                     putString(PrefKeys.DEFAULT_PICTURES_FOLLOW_LIST, JsonMapper.toJson(settings.defaultPicturesFollowList.value))
+                    putString(PrefKeys.DEFAULT_CALENDARS_FOLLOW_LIST, JsonMapper.toJson(settings.defaultCalendarsFollowList.value))
                     putString(PrefKeys.DEFAULT_PRODUCTS_FOLLOW_LIST, JsonMapper.toJson(settings.defaultProductsFollowList.value))
                     putString(PrefKeys.DEFAULT_SHORTS_FOLLOW_LIST, JsonMapper.toJson(settings.defaultShortsFollowList.value))
                     putString(PrefKeys.DEFAULT_PUBLIC_CHATS_FOLLOW_LIST, JsonMapper.toJson(settings.defaultPublicChatsFollowList.value))
@@ -641,6 +643,7 @@ object LocalPreferences {
                         defaultDiscoveryFollowList = MutableStateFlow(followListPrefs.discovery),
                         defaultPollsFollowList = MutableStateFlow(followListPrefs.polls),
                         defaultPicturesFollowList = MutableStateFlow(followListPrefs.pictures),
+                        defaultCalendarsFollowList = MutableStateFlow(followListPrefs.calendars),
                         defaultProductsFollowList = MutableStateFlow(followListPrefs.products),
                         defaultShortsFollowList = MutableStateFlow(followListPrefs.shorts),
                         defaultPublicChatsFollowList = MutableStateFlow(followListPrefs.publicChats),
@@ -712,6 +715,7 @@ object LocalPreferences {
         val discovery: TopFilter,
         val polls: TopFilter,
         val pictures: TopFilter,
+        val calendars: TopFilter,
         val products: TopFilter,
         val shorts: TopFilter,
         val publicChats: TopFilter,
@@ -733,6 +737,7 @@ object LocalPreferences {
             discovery = parseTopFilterOrDefault(getString(PrefKeys.DEFAULT_DISCOVERY_FOLLOW_LIST, null), TopFilter.Global),
             polls = parseTopFilterOrDefault(getString(PrefKeys.DEFAULT_POLLS_FOLLOW_LIST, null), TopFilter.Global),
             pictures = parseTopFilterOrDefault(getString(PrefKeys.DEFAULT_PICTURES_FOLLOW_LIST, null), TopFilter.Global),
+            calendars = parseTopFilterOrDefault(getString(PrefKeys.DEFAULT_CALENDARS_FOLLOW_LIST, null), TopFilter.Global),
             products = parseTopFilterOrDefault(getString(PrefKeys.DEFAULT_PRODUCTS_FOLLOW_LIST, null), TopFilter.AroundMe),
             shorts = parseTopFilterOrDefault(getString(PrefKeys.DEFAULT_SHORTS_FOLLOW_LIST, null), TopFilter.Global),
             publicChats = parseTopFilterOrDefault(getString(PrefKeys.DEFAULT_PUBLIC_CHATS_FOLLOW_LIST, null), TopFilter.Global),

amethyst/src/main/java/com/vitorpamplona/amethyst/model/Account.kt

@@ -489,6 +489,9 @@ class Account(
     val livePicturesFollowLists: StateFlow<IFeedTopNavFilter> = topNavFilterFlow(settings.defaultPicturesFollowList)
     val livePicturesFollowListsPerRelay = OutboxLoaderState(livePicturesFollowLists, cache, scope).flow
 
+    val liveCalendarsFollowLists: StateFlow<IFeedTopNavFilter> = topNavFilterFlow(settings.defaultCalendarsFollowList)
+    val liveCalendarsFollowListsPerRelay = OutboxLoaderState(liveCalendarsFollowLists, cache, scope).flow
+
     val liveProductsFollowLists: StateFlow<IFeedTopNavFilter> = topNavFilterFlow(settings.defaultProductsFollowList)
     val liveProductsFollowListsPerRelay = OutboxLoaderState(liveProductsFollowLists, cache, scope).flow
 

amethyst/src/main/java/com/vitorpamplona/amethyst/model/AccountSettings.kt

@@ -163,6 +163,7 @@ class AccountSettings(
     val defaultDiscoveryFollowList: MutableStateFlow<TopFilter> = MutableStateFlow(TopFilter.Global),
     val defaultPollsFollowList: MutableStateFlow<TopFilter> = MutableStateFlow(TopFilter.Global),
     val defaultPicturesFollowList: MutableStateFlow<TopFilter> = MutableStateFlow(TopFilter.Global),
+    val defaultCalendarsFollowList: MutableStateFlow<TopFilter> = MutableStateFlow(TopFilter.Global),
     val defaultProductsFollowList: MutableStateFlow<TopFilter> = MutableStateFlow(TopFilter.AroundMe),
     val defaultShortsFollowList: MutableStateFlow<TopFilter> = MutableStateFlow(TopFilter.Global),
     val defaultPublicChatsFollowList: MutableStateFlow<TopFilter> = MutableStateFlow(TopFilter.Global),
@@ -529,6 +530,17 @@ class AccountSettings(
         }
     }
 
+    fun changeDefaultCalendarsFollowList(name: FeedDefinition) {
+        changeDefaultCalendarsFollowList(name.code)
+    }
+
+    fun changeDefaultCalendarsFollowList(name: TopFilter) {
+        if (defaultCalendarsFollowList.value != name) {
+            defaultCalendarsFollowList.tryEmit(name)
+            saveAccountSettings()
+        }
+    }
+
     fun changeDefaultProductsFollowList(name: FeedDefinition) {
         changeDefaultProductsFollowList(name.code)
     }

amethyst/src/main/java/com/vitorpamplona/amethyst/service/calendar/CalendarReminderNotifier.kt

@@ -0,0 +1,119 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.service.calendar
+
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.content.Context
+import android.content.Intent
+import androidx.core.app.NotificationCompat
+import androidx.core.app.NotificationManagerCompat
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.ui.MainActivity
+import com.vitorpamplona.amethyst.ui.stringRes
+
+/**
+ * Posts user-visible "starting soon" notifications for NIP-52 appointments the user has RSVP'd
+ * to as ACCEPTED. Mirrors the shape of [com.vitorpamplona.amethyst.service.scheduledposts.ScheduledPostNotifier]
+ * so the two notification surfaces stay consistent.
+ */
+object CalendarReminderNotifier {
+    @Volatile
+    private var channel: NotificationChannel? = null
+    private const val REMINDER_NOT_ID_BASE = 0x80000
+
+    /**
+     * @param eventId   the appointment's event id — used to derive a stable notification id so a
+     *                  second reminder for the same event collapses rather than stacking.
+     * @param title     the appointment title (or a fallback string).
+     * @param body      a short pre-formatted body, e.g. "Starts in 15 minutes".
+     * @param deepLink  a `nostr:naddr…` URI for the calendar event. Tapping the notification
+     *                  hands this to MainActivity, which routes it via `uriToRoute` → the
+     *                  calendar detail screen (CalendarTimeSlotEvent / CalendarDateSlotEvent
+     *                  branches in RouteMaker resolve to Route.CalendarEventDetail).
+     */
+    fun notifyReminder(
+        context: Context,
+        eventId: String,
+        title: String,
+        body: String,
+        deepLink: String,
+    ) {
+        ensureChannel(context)
+        val notId = idFor(eventId)
+        val channelId = stringRes(context, R.string.calendar_reminder_channel_id)
+        val tapIntent =
+            Intent(context, MainActivity::class.java).apply {
+                action = Intent.ACTION_VIEW
+                data = android.net.Uri.parse(deepLink)
+                addFlags(Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TOP)
+            }
+        val tapPendingIntent =
+            PendingIntent.getActivity(
+                context,
+                notId,
+                tapIntent,
+                PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT,
+            )
+        val nm = NotificationManagerCompat.from(context)
+        // POST_NOTIFICATIONS is runtime-granted on Android 13+; bail when denied so the lint
+        // call below doesn't flag and we don't log a misleading no-op.
+        if (!nm.areNotificationsEnabled()) return
+
+        val notification =
+            NotificationCompat
+                .Builder(context, channelId)
+                .setSmallIcon(R.drawable.amethyst)
+                .setContentTitle(title)
+                .setContentText(body)
+                .setStyle(NotificationCompat.BigTextStyle().bigText(body))
+                .setContentIntent(tapPendingIntent)
+                .setPriority(NotificationCompat.PRIORITY_DEFAULT)
+                .setCategory(NotificationCompat.CATEGORY_EVENT)
+                .setAutoCancel(true)
+                .setWhen(System.currentTimeMillis())
+                .build()
+        try {
+            nm.notify(notId, notification)
+        } catch (_: SecurityException) {
+            // Race: permission revoked between the check above and notify().
+        }
+    }
+
+    fun ensureChannel(context: Context) {
+        if (channel != null) return
+        channel =
+            NotificationChannel(
+                stringRes(context, R.string.calendar_reminder_channel_id),
+                stringRes(context, R.string.calendar_reminder_channel_name),
+                NotificationManager.IMPORTANCE_DEFAULT,
+            ).apply {
+                description = stringRes(context, R.string.calendar_reminder_channel_description)
+            }
+        val nm = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
+        nm.createNotificationChannel(channel!!)
+    }
+
+    // Distinct id per event so two reminders for the same event collapse onto one row while
+    // separate events render side by side.
+    private fun idFor(eventId: String): Int = REMINDER_NOT_ID_BASE xor eventId.hashCode()
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/service/calendar/CalendarReminderPrefs.kt

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.service.calendar
+
+import android.content.Context
+import android.content.SharedPreferences
+
+/**
+ * Device-wide preferences for the calendar reminder worker.
+ *
+ * Stored at device scope (rather than per-account) because the worker that consults them runs
+ * globally — multiplexing per-account preferences would require account-context plumbing into
+ * WorkManager that the rest of the app doesn't have. A user who flips between two accounts on
+ * the same device shares the same lead-time and enabled-state. Per-account preferences could be
+ * a follow-up if anyone asks.
+ */
+class CalendarReminderPrefs(
+    context: Context,
+) {
+    private val prefs: SharedPreferences = context.getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE)
+
+    fun isEnabled(): Boolean = prefs.getBoolean(KEY_ENABLED, DEFAULT_ENABLED)
+
+    fun setEnabled(enabled: Boolean) {
+        prefs.edit().putBoolean(KEY_ENABLED, enabled).apply()
+    }
+
+    fun leadMinutes(): Int = prefs.getInt(KEY_LEAD_MINUTES, DEFAULT_LEAD_MINUTES)
+
+    fun setLeadMinutes(minutes: Int) {
+        prefs.edit().putInt(KEY_LEAD_MINUTES, minutes).apply()
+    }
+
+    companion object {
+        const val DEFAULT_LEAD_MINUTES = 15
+        const val DEFAULT_ENABLED = true
+
+        // Choices presented in the settings UI. Anchored to the worker cadence — lead times
+        // smaller than the cadence (15 min) can't be honoured reliably; 60 is the largest the
+        // UX shape supports without an extra "hours" picker.
+        val LEAD_TIME_CHOICES = listOf(5, 15, 30, 60)
+
+        private const val PREF_NAME = "amethyst_calendar_reminder_prefs"
+        private const val KEY_ENABLED = "enabled"
+        private const val KEY_LEAD_MINUTES = "lead_minutes"
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/service/calendar/CalendarReminderStore.kt

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.service.calendar
+
+import android.content.Context
+import android.content.SharedPreferences
+
+/**
+ * Persistent "I've already notified for this event" set. Backed by [SharedPreferences] because
+ * the worker that consults it runs in the app process and the dataset is tiny (≤ a few hundred
+ * IDs at most). Without persistence, every worker run after a restart would re-notify for the
+ * same upcoming event until it started, since LocalCache has no memory of past reminders.
+ *
+ * Keys are event ids (the 32-byte hex from a 31922/31923 appointment). Values aren't used; only
+ * presence in the set matters. Entries are pruned by [forgetBefore] when the worker has just
+ * fired so the store doesn't grow unbounded over time.
+ */
+class CalendarReminderStore(
+    context: Context,
+) {
+    private val prefs: SharedPreferences =
+        context.getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE)
+
+    /**
+     * Returns true when we've previously notified for this exact event-start pairing. If the
+     * author updates the appointment to a new start time, the stored value won't match and
+     * we'll fire a fresh reminder for the new time — that's the desired behaviour: a moved
+     * meeting shouldn't be silently skipped.
+     */
+    fun wasNotified(
+        eventId: String,
+        eventStartSeconds: Long,
+    ): Boolean = prefs.getLong(keyFor(eventId), Long.MIN_VALUE) == eventStartSeconds
+
+    fun markNotified(
+        eventId: String,
+        eventStartSeconds: Long,
+    ) {
+        prefs.edit().putLong(keyFor(eventId), eventStartSeconds).apply()
+    }
+
+    /**
+     * Drops any entry whose recorded event-start time is older than [cutoffSeconds]. Called
+     * after each worker run so the store stays bounded — events that have long since ended
+     * can't fire a second reminder, so their entries are dead weight.
+     */
+    fun forgetBefore(cutoffSeconds: Long) {
+        val editor = prefs.edit()
+        var changed = false
+        prefs.all.forEach { (key, value) ->
+            if (value is Long && value < cutoffSeconds) {
+                editor.remove(key)
+                changed = true
+            }
+        }
+        if (changed) editor.apply()
+    }
+
+    companion object {
+        private const val PREF_NAME = "amethyst_calendar_reminders"
+        private const val KEY_PREFIX = "notified:"
+
+        private fun keyFor(eventId: String) = KEY_PREFIX + eventId
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/service/calendar/CalendarReminderWorker.kt

@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.service.calendar
+
+import android.content.Context
+import androidx.work.CoroutineWorker
+import androidx.work.ExistingPeriodicWorkPolicy
+import androidx.work.PeriodicWorkRequestBuilder
+import androidx.work.WorkManager
+import androidx.work.WorkerParameters
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.appointmentView
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.tags.RSVPStatusTag
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.rsvp.CalendarRSVPEvent
+import com.vitorpamplona.quartz.utils.Log
+import com.vitorpamplona.quartz.utils.TimeUtils
+import java.util.concurrent.TimeUnit
+
+/**
+ * Periodic scan that posts "starting soon" notifications for appointments the user has RSVP'd
+ * to as ACCEPTED.
+ *
+ * The work is bounded — scans LocalCache (which is bounded by the relay subscription) and
+ * consults [CalendarReminderStore] to skip events that have already been notified for. Run as
+ * a 15-minute periodic worker: that's the WorkManager minimum and matches the resolution of
+ * the reminder UI ("starts in ~15 min" is the smallest interval users perceive as "soon").
+ */
+class CalendarReminderWorker(
+    appContext: Context,
+    params: WorkerParameters,
+) : CoroutineWorker(appContext, params) {
+    override suspend fun doWork(): Result {
+        val prefs = CalendarReminderPrefs(applicationContext)
+        if (!prefs.isEnabled()) {
+            Log.d(TAG) { "Reminders disabled; skipping scan." }
+            return Result.success()
+        }
+        val now = TimeUtils.now()
+        val windowEnd = now + prefs.leadMinutes() * 60L
+        val store = CalendarReminderStore(applicationContext)
+
+        // Walk every kind-31925 RSVP authored by an account on this device. We don't have a
+        // multi-account "all logged-in pubkeys" view here, so we accept any RSVP that's
+        // present in cache — the alternative (looking only at the foreground account) would
+        // silently break notifications for account switching during the lead window.
+        val acceptedRsvps =
+            LocalCache.addressables
+                .filterIntoSet { _, note ->
+                    val e = note.event
+                    e is CalendarRSVPEvent && e.status() == RSVPStatusTag.STATUS.ACCEPTED
+                }.mapNotNull { it.event as? CalendarRSVPEvent }
+
+        Log.d(TAG) { "Worker scanning ${acceptedRsvps.size} accepted RSVPs (now=$now, lead=${prefs.leadMinutes()}m)" }
+
+        acceptedRsvps.forEach { rsvp ->
+            val targetAddress = rsvp.calendarEventAddress() ?: return@forEach
+            val targetNote = LocalCache.addressables.get(targetAddress) ?: return@forEach
+            val view = targetNote.appointmentView() ?: return@forEach
+            val start = view.startSeconds ?: return@forEach
+            val eventId =
+                (targetNote.event as? CalendarTimeSlotEvent)?.id
+                    ?: (targetNote.event as? CalendarDateSlotEvent)?.id
+                    ?: return@forEach
+
+            if (start !in now..windowEnd) return@forEach
+            // Keyed on (eventId, start) so a moved appointment re-fires when the new start
+            // enters the lead window — the old notification stays valid in the system tray.
+            if (store.wasNotified(eventId, start)) return@forEach
+
+            val title = view.title ?: stringRes(applicationContext, R.string.calendar_reminder_default_title)
+            val minutesAway = ((start - now).coerceAtLeast(0L) / 60L).toInt()
+            val body =
+                stringRes(
+                    applicationContext,
+                    R.string.calendar_reminder_body,
+                    minutesAway,
+                )
+            val deepLink =
+                "nostr:" +
+                    com.vitorpamplona.quartz.nip19Bech32.entities.NAddress
+                        .create(targetAddress.kind, targetAddress.pubKeyHex, targetAddress.dTag, null)
+            CalendarReminderNotifier.notifyReminder(applicationContext, eventId, title, body, deepLink)
+            store.markNotified(eventId, start)
+            Log.d(TAG) { "Notified $eventId (starts in ${minutesAway}m)" }
+        }
+
+        // Prune entries for events that ended more than a day ago — they can't fire again.
+        store.forgetBefore(now - PRUNE_AGE_SECONDS)
+        return Result.success()
+    }
+
+    companion object {
+        private const val TAG = "CalendarReminderWorker"
+        private const val WORK_NAME = "calendar_reminder_worker"
+
+        // Don't bother remembering "I notified for this" entries for events whose start was
+        // more than a day ago; they can't fire again so the entry is pure overhead.
+        private const val PRUNE_AGE_SECONDS = 24L * 60L * 60L
+
+        fun schedule(context: Context) {
+            val request =
+                PeriodicWorkRequestBuilder<CalendarReminderWorker>(15, TimeUnit.MINUTES)
+                    .build()
+            WorkManager.getInstance(context).enqueueUniquePeriodicWork(
+                WORK_NAME,
+                ExistingPeriodicWorkPolicy.KEEP,
+                request,
+            )
+            Log.d(TAG) { "schedule(): enqueueUniquePeriodicWork($WORK_NAME, 15 MIN, KEEP)" }
+        }
+
+        fun cancel(context: Context) {
+            WorkManager.getInstance(context).cancelUniqueWork(WORK_NAME)
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/service/relayClient/eoseManagers/PerUserAndFollowListEoseManager.kt

@@ -55,6 +55,17 @@ abstract class PerUserAndFollowListEoseManager<T, U : Any>(
 
     fun since(key: T) = latestEOSEs.since(user(key), list(key))
 
+    /**
+     * Drops the EOSE state for the (user, list) pair this key resolves to so the next subscription
+     * assembly will ask the relay from scratch instead of carrying over a stale `since` cursor.
+     * Use when the in-memory note store may have evicted previously-loaded events (e.g.
+     * [LargeSoftCache]'s WeakReference store under memory pressure) and a list switch needs to
+     * re-fetch them rather than rely on a cache that's no longer there.
+     */
+    protected fun clearEoseFor(key: T) {
+        latestEOSEs.clear(user(key), list(key))
+    }
+
     fun newEose(
         key: T,
         relay: NormalizedRelayUrl,

amethyst/src/main/java/com/vitorpamplona/amethyst/service/relayClient/reqCommand/RelaySubscriptionsCoordinator.kt

@@ -31,6 +31,7 @@ import com.vitorpamplona.amethyst.service.relayClient.searchCommand.SearchFilter
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.articles.datasource.ArticlesFilterAssembler
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.badges.datasource.BadgesFilterAssembler
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.badges.profile.datasource.ProfileBadgesFilterAssembler
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.CalendarsFilterAssembler
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.privateDM.datasource.ChatroomFilterAssembler
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.publicChannels.datasource.ChannelFilterAssembler
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.rooms.datasource.ChatroomListFilterAssembler
@@ -111,6 +112,7 @@ class RelaySubscriptionsCoordinator(
 
     val polls = PollsFilterAssembler(client)
     val pictures = PicturesFilterAssembler(client)
+    val calendars = CalendarsFilterAssembler(client)
     val products = ProductsFilterAssembler(client)
     val shorts = ShortsFilterAssembler(client)
     val publicChats = PublicChatsFilterAssembler(client)
@@ -141,6 +143,7 @@ class RelaySubscriptionsCoordinator(
             discovery,
             polls,
             pictures,
+            calendars,
             products,
             shorts,
             publicChats,

amethyst/src/main/java/com/vitorpamplona/amethyst/service/relays/EOSE.kt

@@ -51,6 +51,11 @@ open class EOSEByKey<U : Any>(
 
     fun since(listCode: U) = followList[listCode]?.relayList
 
+    /** Drops the EOSE state for [listCode] so the next filter assembly starts fresh. */
+    fun clear(listCode: U) {
+        followList.remove(listCode)
+    }
+
     fun newEose(
         listCode: U,
         relayUrl: NormalizedRelayUrl,
@@ -83,6 +88,19 @@ open class EOSEAccountKey<U : Any>(
         users.remove(user)
     }
 
+    /**
+     * Drops the EOSE state for the (user, list) pair so the next assembly will ask the relay
+     * from scratch. Used by feeds that need to force a re-fetch — e.g. calendar / pictures
+     * where [LargeSoftCache]'s WeakReference store may have evicted the previously-loaded notes
+     * while the user was viewing a different list.
+     */
+    fun clear(
+        user: User,
+        listCode: U,
+    ) {
+        users[user]?.clear(listCode)
+    }
+
     fun since(
         key: User,
         listCode: U,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/MainActivity.kt

@@ -49,6 +49,8 @@ import com.vitorpamplona.quartz.nip19Bech32.entities.NNote
 import com.vitorpamplona.quartz.nip19Bech32.entities.NProfile
 import com.vitorpamplona.quartz.nip19Bech32.entities.NPub
 import com.vitorpamplona.quartz.nip47WalletConnect.Nip47WalletConnect
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
 import com.vitorpamplona.quartz.utils.Log
 import com.vitorpamplona.quartz.utils.UriParser
 import kotlinx.coroutines.CancellationException
@@ -192,7 +194,7 @@ fun uriToRoute(
                     routeFor(
                         note = LocalCache.getOrCreateAddressableNote(nip19.address()),
                         loggedIn = account,
-                    ) ?: Route.EventRedirect(nip19.aTag())
+                    ) ?: calendarDirectRoute(nip19) ?: Route.EventRedirect(nip19.aTag())
                 }
 
                 is NEmbed -> {
@@ -254,3 +256,19 @@ fun uriToRoute(
 
     return null
 }
+
+/**
+ * Direct route for an `naddr` whose event hasn't arrived in [LocalCache] yet. When a notification
+ * is tapped (or a `nostr:naddr…` deep link arrives) for a calendar appointment we know is kind
+ * 31922/31923, route straight to the dedicated detail screen instead of bouncing through
+ * [Route.EventRedirect]. The detail screen issues its own per-event subscription, so the user
+ * sees the calendar-specific loading placeholder while the event arrives, not the generic
+ * redirect screen.
+ */
+private fun calendarDirectRoute(nip19: NAddress): Route? =
+    when (nip19.kind) {
+        CalendarTimeSlotEvent.KIND,
+        CalendarDateSlotEvent.KIND,
+        -> Route.CalendarEventDetail(nip19.kind, nip19.author, nip19.dTag)
+        else -> null
+    }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/feeds/RememberForeverStates.kt

@@ -65,6 +65,8 @@ object ScrollStateKeys {
     const val BROWSE_EMOJI_SETS_SCREEN = "BrowseEmojiSetsFeed"
     const val COMMUNITIES_LIST = "CommunitiesListFeed"
     const val PICTURES_SCREEN = "PicturesFeed"
+    const val CALENDARS_SCREEN = "CalendarsFeed"
+    const val CALENDAR_COLLECTIONS_SCREEN = "CalendarCollectionsFeed"
     const val PRODUCTS_SCREEN = "ProductsFeed"
     const val SHORTS_SCREEN = "ShortsFeed"
     const val PUBLIC_CHATS_SCREEN = "PublicChatsFeed"

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/AppNavigation.kt

@@ -73,6 +73,12 @@ import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.list.metadat
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.membershipManagement.ArticleBookmarkListManagementScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.membershipManagement.PostBookmarkListManagementScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.old.OldBookmarkListScreen
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.CalendarCollectionsScreen
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.CalendarReminderSettingsScreen
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.CalendarsScreen
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.create.NewCalendarCollectionScreen
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.create.NewCalendarEventScreen
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.detail.CalendarEventDetailScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup.CreateGroupScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup.EditGroupInfoScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup.MarmotGroupChatScreen
@@ -252,6 +258,17 @@ fun BuildNavigation(
         composableFromEnd<Route.ProfileBadges> { ProfileBadgesScreen(accountViewModel, nav) }
         composableFromBottomArgs<Route.AwardBadge> { AwardBadgeScreen(it.kind, it.pubKeyHex, it.dTag, accountViewModel, nav) }
         composableFromEnd<Route.Pictures> { PicturesScreen(accountViewModel, nav) }
+        composableFromEnd<Route.Calendars> { CalendarsScreen(accountViewModel, nav) }
+        composableFromEnd<Route.CalendarCollections> { CalendarCollectionsScreen(accountViewModel, nav) }
+        composableFromEnd<Route.CalendarReminderSettings> { CalendarReminderSettingsScreen(nav) }
+        composableFromEndArgs<Route.CalendarEventDetail> {
+            CalendarEventDetailScreen(it.kind, it.pubKeyHex, it.dTag, accountViewModel, nav)
+        }
+        composableFromBottomArgs<Route.NewCalendarEvent> { NewCalendarEventScreen(nav, accountViewModel) }
+        composableFromBottomArgs<Route.EditCalendarEvent> {
+            NewCalendarEventScreen(nav, accountViewModel, editKind = it.kind, editPubKeyHex = it.pubKeyHex, editDTag = it.dTag)
+        }
+        composableFromBottomArgs<Route.NewCalendarCollection> { NewCalendarCollectionScreen(nav, accountViewModel, it.dTag) }
         composableFromEnd<Route.Products> { ProductsScreen(accountViewModel, nav) }
         composableFromEnd<Route.Shorts> { ShortsScreen(accountViewModel, nav) }
         composableFromEnd<Route.PublicChats> { PublicChatsScreen(accountViewModel, nav) }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/bottombars/NavBarItem.kt

@@ -50,6 +50,8 @@ enum class NavBarItem {
     COMMUNITIES,
     ARTICLES,
     PICTURES,
+    CALENDARS,
+    CALENDAR_COLLECTIONS,
     SHORTS,
     PUBLIC_CHATS,
     FOLLOW_PACKS,
@@ -199,6 +201,20 @@ val NavBarCatalog: Map<NavBarItem, NavBarItemDef> =
                 icon = MaterialSymbols.Photo,
                 resolveRoute = { Route.Pictures },
             ),
+        NavBarItem.CALENDARS to
+            NavBarItemDef(
+                id = NavBarItem.CALENDARS,
+                labelRes = R.string.route_calendars,
+                icon = MaterialSymbols.CalendarMonth,
+                resolveRoute = { Route.Calendars },
+            ),
+        NavBarItem.CALENDAR_COLLECTIONS to
+            NavBarItemDef(
+                id = NavBarItem.CALENDAR_COLLECTIONS,
+                labelRes = R.string.route_calendar_collections,
+                icon = MaterialSymbols.AutoMirrored.FormatListBulleted,
+                resolveRoute = { Route.CalendarCollections },
+            ),
         NavBarItem.SHORTS to
             NavBarItemDef(
                 id = NavBarItem.SHORTS,
@@ -318,6 +334,8 @@ val DrawerFeedsItems: List<NavBarItem> =
         NavBarItem.COMMUNITIES,
         NavBarItem.ARTICLES,
         NavBarItem.PICTURES,
+        NavBarItem.CALENDARS,
+        NavBarItem.CALENDAR_COLLECTIONS,
         NavBarItem.SHORTS,
         NavBarItem.PUBLIC_CHATS,
         NavBarItem.FOLLOW_PACKS,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/routes/RouteMaker.kt

@@ -149,6 +149,18 @@ fun routeForInner(
             Route.GitRepository(noteEvent.kind, noteEvent.pubKey, noteEvent.dTag())
         }
 
+        // Calendar appointments route to their dedicated detail screen rather than the generic
+        // Route.Note that AddressableEvent would fall through to — without this the notification
+        // tap and `nostr:naddr…` deep links land on the bare note view instead of the calendar
+        // detail with RSVPs, participants, and the "in calendars" list.
+        is com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent -> {
+            Route.CalendarEventDetail(noteEvent.kind, noteEvent.pubKey, noteEvent.dTag())
+        }
+
+        is com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent -> {
+            Route.CalendarEventDetail(noteEvent.kind, noteEvent.pubKey, noteEvent.dTag())
+        }
+
         is GiftWrapEvent -> {
             noteEvent.innerEventId?.let {
                 routeFor(LocalCache.getOrCreateNote(it), loggedIn)

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/routes/Routes.kt

@@ -81,6 +81,45 @@ sealed class Route {
 
     @Serializable object Pictures : Route()
 
+    @Serializable object Calendars : Route()
+
+    @Serializable object CalendarCollections : Route()
+
+    @Serializable
+    data class NewCalendarEvent(
+        val draft: String? = null,
+    ) : Route()
+
+    @Serializable
+    data class EditCalendarEvent(
+        val kind: Int,
+        val pubKeyHex: HexKey,
+        val dTag: String,
+    ) : Route() {
+        constructor(address: Address) : this(
+            kind = address.kind,
+            pubKeyHex = address.pubKeyHex,
+            dTag = address.dTag,
+        )
+    }
+
+    @Serializable
+    data class NewCalendarCollection(
+        val dTag: String? = null,
+    ) : Route()
+
+    @Serializable data class CalendarEventDetail(
+        val kind: Int,
+        val pubKeyHex: HexKey,
+        val dTag: String,
+    ) : Route() {
+        constructor(address: Address) : this(
+            kind = address.kind,
+            pubKeyHex = address.pubKeyHex,
+            dTag = address.dTag,
+        )
+    }
+
     @Serializable object Products : Route()
 
     @Serializable object Shorts : Route()
@@ -243,6 +282,8 @@ sealed class Route {
 
     @Serializable object NotificationSettings : Route()
 
+    @Serializable object CalendarReminderSettings : Route()
+
     @Serializable object Lists : Route()
 
     @Serializable data class MyPeopleListView(

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/NoteCompose.kt

@@ -116,7 +116,9 @@ import com.vitorpamplona.amethyst.ui.note.types.RenderAttestorRecommendation
 import com.vitorpamplona.amethyst.ui.note.types.RenderAudioHeader
 import com.vitorpamplona.amethyst.ui.note.types.RenderAudioTrack
 import com.vitorpamplona.amethyst.ui.note.types.RenderBadgeAward
+import com.vitorpamplona.amethyst.ui.note.types.RenderCalendarCollectionEvent
 import com.vitorpamplona.amethyst.ui.note.types.RenderCalendarDateSlotEvent
+import com.vitorpamplona.amethyst.ui.note.types.RenderCalendarRSVPEvent
 import com.vitorpamplona.amethyst.ui.note.types.RenderCalendarTimeSlotEvent
 import com.vitorpamplona.amethyst.ui.note.types.RenderCashuMint
 import com.vitorpamplona.amethyst.ui.note.types.RenderChannelMessage
@@ -254,6 +256,8 @@ import com.vitorpamplona.quartz.nip51Lists.relayLists.TrustedRelayListEvent
 import com.vitorpamplona.quartz.nip51Lists.relaySets.RelaySetEvent
 import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
 import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+import com.vitorpamplona.quartz.nip52Calendar.rsvp.CalendarRSVPEvent
 import com.vitorpamplona.quartz.nip53LiveActivities.chat.LiveActivitiesChatMessageEvent
 import com.vitorpamplona.quartz.nip53LiveActivities.clip.LiveActivitiesClipEvent
 import com.vitorpamplona.quartz.nip53LiveActivities.meetingSpaces.MeetingRoomEvent
@@ -1189,6 +1193,14 @@ private fun RenderNoteRow(
             RenderCalendarDateSlotEvent(baseNote, accountViewModel, nav)
         }
 
+        is CalendarEvent -> {
+            RenderCalendarCollectionEvent(baseNote, accountViewModel, nav)
+        }
+
+        is CalendarRSVPEvent -> {
+            RenderCalendarRSVPEvent(baseNote, accountViewModel, nav)
+        }
+
         is GoalEvent -> {
             RenderGoal(baseNote, accountViewModel, nav)
         }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/CalendarCollectionRender.kt

@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.note.types
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
+import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.amethyst.ui.theme.StdVertSpacer
+import com.vitorpamplona.amethyst.ui.theme.replyModifier
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+
+@Composable
+fun RenderCalendarCollectionEvent(
+    note: Note,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    val event = note.event as? CalendarEvent ?: return
+
+    Column(MaterialTheme.colorScheme.replyModifier) {
+        Row(
+            modifier = Modifier.fillMaxWidth().padding(start = 10.dp, end = 10.dp, top = 10.dp),
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
+            Icon(
+                symbol = MaterialSymbols.CalendarMonth,
+                contentDescription = null,
+                modifier = Modifier.size(24.dp),
+                tint = MaterialTheme.colorScheme.primary,
+            )
+            Spacer(modifier = Modifier.size(8.dp))
+            Text(
+                text = event.title() ?: "—",
+                style = MaterialTheme.typography.titleMedium,
+                fontWeight = FontWeight.SemiBold,
+                maxLines = 2,
+                overflow = TextOverflow.Ellipsis,
+            )
+        }
+
+        if (event.content.isNotBlank()) {
+            Spacer(modifier = StdVertSpacer)
+            Text(
+                text = event.content,
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.fillMaxWidth().padding(horizontal = 10.dp),
+                maxLines = 4,
+                overflow = TextOverflow.Ellipsis,
+            )
+        }
+
+        Spacer(modifier = StdVertSpacer)
+        Text(
+            text = stringRes(R.string.calendar_collection_count, event.calendarEventAddresses().size),
+            style = MaterialTheme.typography.labelMedium,
+            color = MaterialTheme.colorScheme.primary,
+            modifier = Modifier.padding(start = 10.dp, end = 10.dp, bottom = 12.dp),
+        )
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/CalendarEvent.kt

@@ -86,6 +86,15 @@ fun RenderCalendarTimeSlotEvent(
         dateRange = dateRange,
         note = note,
         accountViewModel = accountViewModel,
+        rsvpRow = {
+            CalendarRsvpRow(
+                eventKind = CalendarTimeSlotEvent.KIND,
+                eventPubKey = noteEvent.pubKey,
+                eventDTag = noteEvent.dTag(),
+                eventId = noteEvent.id,
+                accountViewModel = accountViewModel,
+            )
+        },
     )
 }
 
@@ -119,6 +128,15 @@ fun RenderCalendarDateSlotEvent(
         dateRange = dateRange,
         note = note,
         accountViewModel = accountViewModel,
+        rsvpRow = {
+            CalendarRsvpRow(
+                eventKind = CalendarDateSlotEvent.KIND,
+                eventPubKey = noteEvent.pubKey,
+                eventDTag = noteEvent.dTag(),
+                eventId = noteEvent.id,
+                accountViewModel = accountViewModel,
+            )
+        },
     )
 }
 
@@ -131,6 +149,7 @@ private fun CalendarHeader(
     dateRange: String?,
     note: Note,
     accountViewModel: AccountViewModel,
+    rsvpRow: @Composable () -> Unit = {},
 ) {
     Column(MaterialTheme.colorScheme.replyModifier) {
         image?.let {
@@ -209,6 +228,8 @@ private fun CalendarHeader(
         if (summary == null) {
             Spacer(modifier = StdVertSpacer)
         }
+
+        rsvpRow()
     }
 }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/CalendarRsvpRender.kt

@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.note.types
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
+import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.amethyst.ui.theme.StdVertSpacer
+import com.vitorpamplona.amethyst.ui.theme.replyModifier
+import com.vitorpamplona.quartz.nip52Calendar.appt.tags.RSVPStatusTag
+import com.vitorpamplona.quartz.nip52Calendar.rsvp.CalendarRSVPEvent
+
+@Composable
+fun RenderCalendarRSVPEvent(
+    note: Note,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    val event = note.event as? CalendarRSVPEvent ?: return
+    val status = event.status()
+    val targetAddress = event.calendarEventAddress()
+    val freebusy = event.freebusy()
+
+    val statusLabel =
+        when (status) {
+            RSVPStatusTag.STATUS.ACCEPTED -> stringRes(R.string.calendar_rsvp_going)
+            RSVPStatusTag.STATUS.TENTATIVE -> stringRes(R.string.calendar_rsvp_maybe)
+            RSVPStatusTag.STATUS.DECLINED -> stringRes(R.string.calendar_rsvp_not_going)
+            null -> "—"
+        }
+
+    val statusColor =
+        when (status) {
+            RSVPStatusTag.STATUS.ACCEPTED -> MaterialTheme.colorScheme.primary
+            RSVPStatusTag.STATUS.TENTATIVE -> MaterialTheme.colorScheme.tertiary
+            RSVPStatusTag.STATUS.DECLINED -> MaterialTheme.colorScheme.error
+            null -> Color.Gray
+        }
+
+    Column(MaterialTheme.colorScheme.replyModifier) {
+        Row(
+            modifier = Modifier.fillMaxWidth().padding(start = 10.dp, end = 10.dp, top = 10.dp),
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
+            Icon(
+                symbol = MaterialSymbols.CalendarMonth,
+                contentDescription = null,
+                modifier = Modifier.size(20.dp),
+                tint = statusColor,
+            )
+            Spacer(modifier = Modifier.size(8.dp))
+            Text(
+                text = statusLabel,
+                style = MaterialTheme.typography.titleMedium,
+                fontWeight = FontWeight.SemiBold,
+                color = statusColor,
+            )
+        }
+
+        if (event.content.isNotBlank()) {
+            Spacer(modifier = StdVertSpacer)
+            Text(
+                text = event.content,
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.padding(start = 10.dp, end = 10.dp),
+            )
+        }
+
+        targetAddress?.let { addr ->
+            Spacer(modifier = StdVertSpacer)
+            Text(
+                text = "→ ${addr.toValue()}",
+                style = MaterialTheme.typography.labelSmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.padding(start = 10.dp, end = 10.dp, bottom = 12.dp),
+            )
+        }
+
+        if (freebusy != null) {
+            Spacer(modifier = StdVertSpacer)
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/CalendarRsvpRow.kt

@@ -0,0 +1,187 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.note.types
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.ButtonDefaults
+import androidx.compose.material3.FilledTonalButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip01Core.tags.aTag.ATag
+import com.vitorpamplona.quartz.nip01Core.tags.people.PTag
+import com.vitorpamplona.quartz.nip52Calendar.appt.tags.RSVPStatusTag
+import com.vitorpamplona.quartz.nip52Calendar.rsvp.CalendarRSVPEvent
+
+/**
+ * Renders a 3-button RSVP row (Going / Maybe / Can't go) below a NIP-52 calendar appointment.
+ *
+ * Uses a deterministic d-tag derived from the target appointment's address so the user has
+ * exactly one RSVP per event from this client — tapping again replaces it rather than appending
+ * another addressable. The button matching the current status renders as filled-tonal; the
+ * others render outlined.
+ */
+@Composable
+fun CalendarRsvpRow(
+    eventKind: Int,
+    eventPubKey: String,
+    eventDTag: String,
+    eventId: String,
+    accountViewModel: AccountViewModel,
+) {
+    val myPubKey = accountViewModel.userProfile().pubkeyHex
+    val targetAddress = remember(eventKind, eventPubKey, eventDTag) { Address(eventKind, eventPubKey, eventDTag) }
+    val myRsvpAddress = remember(targetAddress, myPubKey) { rsvpAddressFor(myPubKey, targetAddress) }
+
+    val myRsvpNote = remember(myRsvpAddress) { LocalCache.getOrCreateAddressableNote(myRsvpAddress) }
+    val myRsvpState by myRsvpNote
+        .flow()
+        .metadata.stateFlow
+        .collectAsStateWithLifecycle()
+
+    val currentStatus = (myRsvpState.note.event as? CalendarRSVPEvent)?.status()
+
+    val onTap: (RSVPStatusTag.STATUS) -> Unit = { newStatus ->
+        sendRsvp(
+            accountViewModel = accountViewModel,
+            targetAddress = targetAddress,
+            eventId = eventId,
+            myPubKey = myPubKey,
+            status = newStatus,
+        )
+    }
+
+    Row(
+        modifier = Modifier.fillMaxWidth().padding(start = 10.dp, end = 10.dp, top = 10.dp, bottom = 12.dp),
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        RsvpButton(
+            label = stringRes(R.string.calendar_rsvp_going),
+            status = RSVPStatusTag.STATUS.ACCEPTED,
+            currentStatus = currentStatus,
+            modifier = Modifier.weight(1f),
+            onClick = onTap,
+        )
+        RsvpButton(
+            label = stringRes(R.string.calendar_rsvp_maybe),
+            status = RSVPStatusTag.STATUS.TENTATIVE,
+            currentStatus = currentStatus,
+            modifier = Modifier.weight(1f),
+            onClick = onTap,
+        )
+        RsvpButton(
+            label = stringRes(R.string.calendar_rsvp_not_going),
+            status = RSVPStatusTag.STATUS.DECLINED,
+            currentStatus = currentStatus,
+            modifier = Modifier.weight(1f),
+            onClick = onTap,
+        )
+    }
+}
+
+@Composable
+private fun RsvpButton(
+    label: String,
+    status: RSVPStatusTag.STATUS,
+    currentStatus: RSVPStatusTag.STATUS?,
+    modifier: Modifier,
+    onClick: (RSVPStatusTag.STATUS) -> Unit,
+) {
+    val selected = status == currentStatus
+    if (selected) {
+        FilledTonalButton(
+            onClick = { onClick(status) },
+            modifier = modifier,
+            colors =
+                ButtonDefaults.filledTonalButtonColors(
+                    containerColor = colorFor(status),
+                    contentColor = Color.White,
+                ),
+        ) {
+            Text(text = label)
+        }
+    } else {
+        OutlinedButton(
+            onClick = { onClick(status) },
+            modifier = modifier,
+        ) {
+            Text(text = label)
+        }
+    }
+}
+
+@Composable
+private fun colorFor(status: RSVPStatusTag.STATUS) =
+    when (status) {
+        RSVPStatusTag.STATUS.ACCEPTED -> MaterialTheme.colorScheme.primary
+        RSVPStatusTag.STATUS.TENTATIVE -> MaterialTheme.colorScheme.tertiary
+        RSVPStatusTag.STATUS.DECLINED -> MaterialTheme.colorScheme.error
+    }
+
+/**
+ * Deterministic per-target d-tag so each user's RSVP for a given event is a single addressable.
+ * The format mirrors the a-tag coordinate so it's debuggable (`rsvp:31923:<pubkey>:<dtag>`).
+ */
+fun rsvpDTagFor(targetAddress: Address): String = "rsvp:${targetAddress.kind}:${targetAddress.pubKeyHex}:${targetAddress.dTag}"
+
+fun rsvpAddressFor(
+    myPubKey: String,
+    targetAddress: Address,
+): Address = Address(CalendarRSVPEvent.KIND, myPubKey, rsvpDTagFor(targetAddress))
+
+private fun sendRsvp(
+    accountViewModel: AccountViewModel,
+    targetAddress: Address,
+    eventId: String,
+    myPubKey: String,
+    status: RSVPStatusTag.STATUS,
+) {
+    val relayHint = LocalCache.getNoteIfExists(eventId)?.relays?.firstOrNull()
+    val aTag = ATag(targetAddress, relayHint)
+    val pTag = PTag(targetAddress.pubKeyHex)
+    val dTag = rsvpDTagFor(targetAddress)
+
+    accountViewModel.launchSigner {
+        accountViewModel.account.signAndComputeBroadcast(
+            CalendarRSVPEvent.build(
+                calendarEventAddress = aTag,
+                status = status,
+                calendarEventAuthor = pTag,
+                dTag = dTag,
+            ),
+        )
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/AccountFeedContentStates.kt

@@ -30,6 +30,8 @@ import com.vitorpamplona.amethyst.ui.feeds.ChannelFeedContentState
 import com.vitorpamplona.amethyst.ui.screen.TopNavFilterState
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.articles.dal.ArticlesFeedFilter
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.badges.dal.BadgesFeedFilter
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal.CalendarAppointmentsFeedFilter
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal.CalendarCollectionsFeedFilter
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.rooms.dal.ChatroomListKnownFeedFilter
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.rooms.dal.ChatroomListNewFeedFilter
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.communities.list.dal.CommunitiesFeedFilter
@@ -99,6 +101,8 @@ class AccountFeedContentStates(
     val communitiesList = FeedContentState(CommunitiesFeedFilter(account), scope, LocalCache)
 
     val picturesFeed = FeedContentState(PictureFeedFilter(account), scope, LocalCache)
+    val calendarAppointmentsFeed = FeedContentState(CalendarAppointmentsFeedFilter(account), scope, LocalCache)
+    val calendarCollectionsFeed = FeedContentState(CalendarCollectionsFeedFilter(account), scope, LocalCache)
     val productsFeed = FeedContentState(ProductsFeedFilter(account), scope, LocalCache)
     val shortsFeed = FeedContentState(ShortsFeedFilter(account), scope, LocalCache)
     val publicChatsFeed = FeedContentState(PublicChatsFeedFilter(account), scope, LocalCache)
@@ -196,6 +200,9 @@ class AccountFeedContentStates(
         longsFeed.updateFeedWith(newNotes)
         articlesFeed.updateFeedWith(newNotes)
 
+        calendarAppointmentsFeed.updateFeedWith(newNotes)
+        calendarCollectionsFeed.updateFeedWith(newNotes)
+
         notifications.updateFeedWith(newNotes)
         if (account.settings.splitNotificationsEnabled.value) {
             notificationsFollowing.updateFeedWith(newNotes)
@@ -248,6 +255,9 @@ class AccountFeedContentStates(
         longsFeed.deleteFromFeed(newNotes)
         articlesFeed.deleteFromFeed(newNotes)
 
+        calendarAppointmentsFeed.deleteFromFeed(newNotes)
+        calendarCollectionsFeed.deleteFromFeed(newNotes)
+
         notifications.deleteFromFeed(newNotes)
         if (account.settings.splitNotificationsEnabled.value) {
             notificationsFollowing.deleteFromFeed(newNotes)

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/BottomBarFeedPreloaders.kt

@@ -27,6 +27,7 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.vitorpamplona.amethyst.ui.navigation.bottombars.NavBarItem
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.articles.datasource.ArticlesFilterAssemblerSubscription
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.badges.datasource.BadgesFilterAssemblerSubscription
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.CalendarsFilterAssemblerSubscription
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.rooms.datasource.ChatroomListFilterAssemblerSubscription
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.communities.list.datasource.CommunitiesListFilterAssemblerSubscription
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.discover.datasource.DiscoveryFilterAssemblerSubscription
@@ -85,6 +86,10 @@ private fun PreloadFor(
 
         NavBarItem.PICTURES -> PicturesFilterAssemblerSubscription(accountViewModel)
 
+        NavBarItem.CALENDARS,
+        NavBarItem.CALENDAR_COLLECTIONS,
+        -> CalendarsFilterAssemblerSubscription(accountViewModel)
+
         NavBarItem.SHORTS -> ShortsFilterAssemblerSubscription(accountViewModel)
 
         NavBarItem.PUBLIC_CHATS -> PublicChatsFilterAssemblerSubscription(accountViewModel)

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/AddToPhoneCalendar.kt

@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import android.content.ActivityNotFoundException
+import android.content.Context
+import android.content.Intent
+import android.provider.CalendarContract
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.parseIsoDateToUnixSeconds
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+
+/**
+ * Opens the system "New Event" composer (Google Calendar / Samsung / iCloud / etc.) pre-populated
+ * with this appointment's title, time, location, and description. The user sees their normal
+ * calendar UI with one tap to "Save" — strictly nicer than the .ics-via-share-sheet path because
+ * it doesn't go through a file and surfaces the user's preferred calendar app directly.
+ *
+ * Returns true if a calendar app handled the intent, false if no handler was found — the caller
+ * can decide whether to fall back to the .ics share path.
+ */
+fun addToPhoneCalendar(
+    context: Context,
+    event: Event,
+): Boolean {
+    val (title, location, summary) =
+        when (event) {
+            is CalendarTimeSlotEvent -> Triple(event.title(), event.location(), event.summary())
+            is CalendarDateSlotEvent -> Triple(event.title(), event.location(), event.summary())
+            else -> return false
+        }
+    val (beginMs, endMs, allDay) = computeRangeMs(event) ?: return false
+
+    val description =
+        buildString {
+            summary?.let { append(it) }
+            if (event.content.isNotBlank()) {
+                if (isNotEmpty()) append("\n\n")
+                append(event.content)
+            }
+        }
+
+    val intent =
+        Intent(Intent.ACTION_INSERT).apply {
+            data = CalendarContract.Events.CONTENT_URI
+            putExtra(CalendarContract.Events.TITLE, title.orEmpty())
+            location?.let { putExtra(CalendarContract.Events.EVENT_LOCATION, it) }
+            if (description.isNotEmpty()) {
+                putExtra(CalendarContract.Events.DESCRIPTION, description)
+            }
+            putExtra(CalendarContract.EXTRA_EVENT_BEGIN_TIME, beginMs)
+            putExtra(CalendarContract.EXTRA_EVENT_END_TIME, endMs)
+            putExtra(CalendarContract.EXTRA_EVENT_ALL_DAY, allDay)
+            addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+        }
+
+    return try {
+        context.startActivity(intent)
+        true
+    } catch (_: ActivityNotFoundException) {
+        false
+    }
+}
+
+/**
+ * Computes the (beginMillis, endMillis, isAllDay) triple from a calendar event. NIP-52 date-slot
+ * uses ISO dates that we anchor at local midnight; time-slot uses unix seconds. End defaults to
+ * begin + 1 hour for time-slot events without an end and to begin + 1 day for all-day events
+ * without an end (calendar providers expect end > start for any visible event).
+ */
+private fun computeRangeMs(event: Event): Triple<Long, Long, Boolean>? =
+    when (event) {
+        is CalendarTimeSlotEvent -> {
+            val start = event.start() ?: return null
+            val end = event.end() ?: (start + 3600L)
+            Triple(start * 1000L, end * 1000L, false)
+        }
+        is CalendarDateSlotEvent -> {
+            val startSec = parseIsoDateToUnixSeconds(event.start()) ?: return null
+            val endSec = parseIsoDateToUnixSeconds(event.end()) ?: (startSec + 86400L)
+            Triple(startSec * 1000L, endSec * 1000L, true)
+        }
+        else -> null
+    }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarCollectionsScreen.kt

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedContentState
+import com.vitorpamplona.amethyst.ui.feeds.WatchLifecycleAndUpdateModel
+import com.vitorpamplona.amethyst.ui.layouts.DisappearingScaffold
+import com.vitorpamplona.amethyst.ui.navigation.bottombars.AppBottomBar
+import com.vitorpamplona.amethyst.ui.navigation.bottombars.FabBottomBarPadded
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.CalendarsFilterAssemblerSubscription
+
+/**
+ * Top-level screen for browsing NIP-52 kind-31924 calendars (collections of appointments). Reuses
+ * the [CalendarsFilterAssembler] subscription so opening this screen also keeps the appointment
+ * subscription warm — both feeds share one relay subscription.
+ */
+@Composable
+fun CalendarCollectionsScreen(
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    CalendarCollectionsScreen(
+        feedState = accountViewModel.feedStates.calendarCollectionsFeed,
+        accountViewModel = accountViewModel,
+        nav = nav,
+    )
+}
+
+@Composable
+fun CalendarCollectionsScreen(
+    feedState: FeedContentState,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    WatchLifecycleAndUpdateModel(feedState)
+    WatchAccountForCalendarCollectionsScreen(feedState, accountViewModel)
+    CalendarsFilterAssemblerSubscription(accountViewModel)
+
+    DisappearingScaffold(
+        isInvertedLayout = false,
+        topBar = {
+            CalendarCollectionsTopBar(accountViewModel, nav)
+        },
+        bottomBar = {
+            AppBottomBar(Route.CalendarCollections, nav, accountViewModel) { route ->
+                if (route == Route.CalendarCollections) {
+                    feedState.sendToTop()
+                } else {
+                    nav.navBottomBar(route)
+                }
+            }
+        },
+        floatingButton = {
+            FabBottomBarPadded(nav) {
+                NewCalendarButton(nav)
+            }
+        },
+        accountViewModel = accountViewModel,
+    ) {
+        CalendarCollectionsView(feedState, accountViewModel, nav)
+    }
+}
+
+@Composable
+private fun WatchAccountForCalendarCollectionsScreen(
+    feedState: FeedContentState,
+    accountViewModel: AccountViewModel,
+) {
+    val listState by accountViewModel.account.liveCalendarsFollowLists.collectAsStateWithLifecycle()
+    val hiddenUsers by
+        accountViewModel.account.hiddenUsers.flow
+            .collectAsStateWithLifecycle()
+
+    LaunchedEffect(accountViewModel, listState, hiddenUsers) {
+        feedState.checkKeysInvalidateDataAndSendToTop()
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarCollectionsTopBar.kt

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.model.TopFilter
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.topbars.FeedFilterSpinner
+import com.vitorpamplona.amethyst.ui.navigation.topbars.UserDrawerSearchTopBar
+import com.vitorpamplona.amethyst.ui.screen.FeedDefinition
+import com.vitorpamplona.amethyst.ui.screen.TopNavFilterState
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+
+@Composable
+fun CalendarCollectionsTopBar(
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    UserDrawerSearchTopBar(accountViewModel, nav) {
+        val list by accountViewModel.account.settings.defaultCalendarsFollowList
+            .collectAsStateWithLifecycle()
+
+        CalendarCollectionsTopNavFilterBar(
+            followListsModel = accountViewModel.feedStates.feedListOptions,
+            listName = list,
+            accountViewModel = accountViewModel,
+            onChange = accountViewModel.account.settings::changeDefaultCalendarsFollowList,
+        )
+    }
+}
+
+@Composable
+private fun CalendarCollectionsTopNavFilterBar(
+    followListsModel: TopNavFilterState,
+    listName: TopFilter,
+    accountViewModel: AccountViewModel,
+    onChange: (FeedDefinition) -> Unit,
+) {
+    val allLists by followListsModel.kind3GlobalPeopleRoutes.collectAsStateWithLifecycle()
+
+    FeedFilterSpinner(
+        placeholderCode = listName,
+        explainer = stringRes(R.string.select_list_to_filter),
+        options = allLists,
+        onSelect = onChange,
+        accountViewModel = accountViewModel,
+    )
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarCollectionsView.kt

@@ -0,0 +1,230 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.Card
+import androidx.compose.material3.CardDefaults
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
+import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.IcsExport
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedContentState
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedState
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.ui.feeds.RefresheableBox
+import com.vitorpamplona.amethyst.ui.layouts.rememberFeedContentPadding
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.video.UserCardHeader
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.amethyst.ui.theme.FeedPadding
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+@Composable
+fun CalendarCollectionsView(
+    feedState: FeedContentState,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    RefresheableBox(feedState, true) {
+        val state by feedState.feedContent.collectAsStateWithLifecycle()
+
+        when (val s = state) {
+            is FeedState.Loaded -> CollectionsBody(s, accountViewModel, nav)
+            is FeedState.Empty -> EmptyCollections()
+            is FeedState.Loading -> Box(modifier = Modifier.fillMaxSize())
+            is FeedState.FeedError ->
+                Box(
+                    modifier = Modifier.fillMaxSize().padding(32.dp),
+                    contentAlignment = Alignment.Center,
+                ) {
+                    Text(
+                        text = s.errorMessage,
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.error,
+                    )
+                }
+        }
+    }
+}
+
+@Composable
+private fun CollectionsBody(
+    loaded: FeedState.Loaded,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    val items by loaded.feed.collectAsStateWithLifecycle()
+    LazyColumn(
+        // Reserve top space for the surrounding [DisappearingScaffold]'s top bar — without this
+        // the first card scrolls under it on the initial render.
+        contentPadding = rememberFeedContentPadding(FeedPadding),
+        modifier = Modifier.fillMaxSize(),
+    ) {
+        items(items.list, key = { it.idHex }) { note ->
+            CalendarCollectionCard(note, accountViewModel, nav)
+        }
+    }
+}
+
+@Composable
+private fun EmptyCollections() {
+    CalendarEmptyState(
+        title = stringRes(R.string.calendar_empty_collections_title),
+        subtitle = stringRes(R.string.calendar_empty_collections_subtitle),
+    )
+}
+
+@Composable
+fun CalendarCollectionCard(
+    note: Note,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    val event = note.event as? CalendarEvent ?: return
+    val title = remember(note.idHex) { event.title() }
+    val description = remember(note.idHex) { event.content.take(180) }
+    val count = remember(note.idHex) { event.calendarEventAddresses().size }
+    val context = LocalContext.current
+
+    // Calendar collections are addressable (kind 31924); route to the dedicated
+    // CalendarEventDetail screen instead of the generic Route.Note thread view, which
+    // didn't know how to render them as a list of member appointments.
+    val collectionRoute = remember(note.idHex, event) { Route.CalendarEventDetail(event.address()) }
+    Card(
+        modifier =
+            Modifier
+                .fillMaxWidth()
+                .padding(horizontal = 12.dp, vertical = 6.dp)
+                .clickable { nav.nav(collectionRoute) },
+        shape = RoundedCornerShape(14.dp),
+        colors = CardDefaults.elevatedCardColors(),
+        elevation = CardDefaults.elevatedCardElevation(defaultElevation = 2.dp),
+    ) {
+        // Author header matches every other social card in the app, but without the createdAt
+        // timestamp — the user cares about the collection's events, not when the metadata was
+        // last edited.
+        UserCardHeader(
+            baseNote = note,
+            accountViewModel = accountViewModel,
+            nav = nav,
+            showTimeAgo = false,
+        )
+        Row(
+            modifier = Modifier.padding(start = 14.dp, end = 14.dp, bottom = 14.dp),
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
+            Icon(
+                symbol = MaterialSymbols.CalendarMonth,
+                contentDescription = null,
+                modifier = Modifier.size(32.dp),
+                tint = MaterialTheme.colorScheme.primary,
+            )
+            Column(
+                modifier = Modifier.weight(1f).padding(start = 14.dp),
+                verticalArrangement = Arrangement.spacedBy(4.dp),
+            ) {
+                Text(
+                    text = title ?: "—",
+                    style = MaterialTheme.typography.titleMedium,
+                    fontWeight = FontWeight.SemiBold,
+                    maxLines = 2,
+                    overflow = TextOverflow.Ellipsis,
+                )
+                if (description.isNotBlank()) {
+                    Text(
+                        text = description,
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        maxLines = 2,
+                        overflow = TextOverflow.Ellipsis,
+                    )
+                }
+                Text(
+                    text = stringRes(R.string.calendar_collection_count, count),
+                    style = MaterialTheme.typography.labelMedium,
+                    color = MaterialTheme.colorScheme.primary,
+                )
+            }
+            IconButton(onClick = {
+                val members = collectMembers(event)
+                val ics = IcsExport.calendarToIcs(event, members, TimeUtils.now())
+                val filename = IcsExport.calendarFilename(event)
+                shareIcs(context, filename, ics)
+            }) {
+                Icon(
+                    symbol = MaterialSymbols.Share,
+                    contentDescription = stringRes(R.string.calendar_export_event),
+                    modifier = Modifier.size(20.dp),
+                    tint = MaterialTheme.colorScheme.onSurfaceVariant,
+                )
+            }
+        }
+    }
+}
+
+/**
+ * Resolves a calendar's member addresses to their cached events, skipping members that haven't
+ * arrived from relays yet or aren't appointments. Returns a list compatible with
+ * [IcsExport.calendarToIcs].
+ */
+private fun collectMembers(calendar: CalendarEvent): List<Pair<Address, Any>> =
+    calendar
+        .calendarEventAddresses()
+        .mapNotNull { addr ->
+            val cachedEvent = LocalCache.addressables.get(addr)?.event
+            if (cachedEvent is CalendarTimeSlotEvent || cachedEvent is CalendarDateSlotEvent) {
+                addr to cachedEvent
+            } else {
+                null
+            }
+        }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarDayView.kt

@@ -0,0 +1,233 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.derivedStateOf
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.appointmentView
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.calendarLocalDayKeyRange
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.groupByDayKeyExpanded
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedContentState
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedState
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.ui.layouts.rememberFeedContentPadding
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.amethyst.ui.theme.FeedPadding
+import java.time.LocalDate
+import java.time.ZoneId
+
+@Composable
+fun CalendarDayView(
+    feedState: FeedContentState,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+    filterAddresses: Set<com.vitorpamplona.quartz.nip01Core.core.Address>? = null,
+) {
+    val state by feedState.feedContent.collectAsStateWithLifecycle()
+    val notes =
+        when (val s = state) {
+            is FeedState.Loaded ->
+                s.feed
+                    .collectAsStateWithLifecycle()
+                    .value.list
+                    .applyCalendarFilter(filterAddresses)
+            else -> emptyList()
+        }
+
+    val today = remember { LocalDate.now() }
+    // Persisting an epoch-day Long is auto-saveable; arithmetic in [LocalDate] is DST-safe
+    // (millisecond stepping was off by an hour after spring/fall transitions).
+    var visibleEpochDay by rememberSaveable { mutableStateOf(today.toEpochDay()) }
+    val visibleDate = LocalDate.ofEpochDay(visibleEpochDay)
+
+    val byDay by remember(notes) { derivedStateOf { groupByDayKeyExpanded(notes) } }
+    val dayEvents = byDay[visibleDate.toEpochDay()].orEmpty()
+
+    val sorted =
+        remember(dayEvents) {
+            // All-day events bubble to the top (Long.MIN_VALUE), then time-slot events in order.
+            dayEvents.sortedBy { it.appointmentView()?.startSeconds ?: Long.MAX_VALUE }
+        }
+
+    // Single LazyColumn — nav header is the first item so it scrolls with the disappearing
+    // top bar instead of staying pinned mid-screen when the bar collapses.
+    LazyColumn(
+        contentPadding = rememberFeedContentPadding(FeedPadding),
+        modifier =
+            Modifier
+                .fillMaxSize()
+                .calendarSwipeNavigation(
+                    key = visibleEpochDay,
+                    onSwipeLeft = { visibleEpochDay = visibleDate.plusDays(1).toEpochDay() },
+                    onSwipeRight = { visibleEpochDay = visibleDate.minusDays(1).toEpochDay() },
+                ),
+    ) {
+        item(key = "day-nav") {
+            CalendarNavigationHeader(
+                title = formatLongDate(visibleDate.atStartOfDay(ZoneId.systemDefault()).toEpochSecond()),
+                prevContentDescription = stringRes(R.string.calendar_nav_previous_day),
+                nextContentDescription = stringRes(R.string.calendar_nav_next_day),
+                onPrev = { visibleEpochDay = visibleDate.minusDays(1).toEpochDay() },
+                onNext = { visibleEpochDay = visibleDate.plusDays(1).toEpochDay() },
+                onToday = { visibleEpochDay = LocalDate.now().toEpochDay() },
+            )
+        }
+
+        if (dayEvents.isEmpty()) {
+            item(key = "day-empty") {
+                CalendarEmptyState(
+                    title = stringRes(R.string.calendar_empty_day_title),
+                    subtitle = stringRes(R.string.calendar_empty_day_subtitle),
+                )
+            }
+        } else {
+            items(sorted, key = { it.idHex }) { note ->
+                Column(modifier = Modifier.padding(horizontal = 12.dp)) {
+                    DayRow(
+                        note = note,
+                        visibleEpochDay = visibleEpochDay,
+                        onClick = { nav.nav(Route.Note(note.idHex)) },
+                    )
+                    HorizontalDivider()
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun DayRow(
+    note: Note,
+    visibleEpochDay: Long,
+    onClick: () -> Unit,
+) {
+    val view = note.appointmentView() ?: return
+    val range = note.calendarLocalDayKeyRange()
+    // Position within a multi-day event: today is "Day 2 of 4". Renders below the time label so
+    // a continuation day on a 3-day conference reads as "9:00 AM / Day 2 of 3" rather than
+    // looking like a fresh event.
+    val dayOfTotal =
+        if (range != null && range.last > range.first) {
+            (visibleEpochDay - range.first + 1).toInt() to (range.last - range.first + 1).toInt()
+        } else {
+            null
+        }
+
+    val startSeconds = view.startSeconds
+    val timeLabel =
+        when {
+            view.isAllDay -> stringRes(R.string.calendar_all_day)
+            startSeconds != null && visibleEpochDay > (range?.first ?: visibleEpochDay) ->
+                // Continuation day of a multi-day timed event — the "9:00 AM" of day 1 is
+                // misleading on day 2 since the event has been ongoing overnight. Show a
+                // continuation marker so the user reads it as "still happening".
+                stringRes(R.string.calendar_continues)
+            startSeconds != null -> formatTimeOfDay(startSeconds)
+            else -> "—"
+        }
+
+    Row(
+        modifier =
+            Modifier
+                .fillMaxWidth()
+                .clickable(onClick = onClick)
+                .padding(vertical = 10.dp),
+        verticalAlignment = Alignment.Top,
+    ) {
+        Text(
+            text = timeLabel,
+            style = MaterialTheme.typography.bodyMedium,
+            fontWeight = FontWeight.SemiBold,
+            color = MaterialTheme.colorScheme.primary,
+            modifier = Modifier.width(72.dp),
+        )
+        Box(
+            modifier =
+                Modifier
+                    .width(3.dp)
+                    .height(40.dp)
+                    .background(MaterialTheme.colorScheme.primary, RoundedCornerShape(2.dp)),
+        )
+        Column(
+            modifier = Modifier.padding(start = 12.dp),
+            verticalArrangement = Arrangement.spacedBy(2.dp),
+        ) {
+            view.title?.let {
+                Text(
+                    text = it,
+                    style = MaterialTheme.typography.bodyLarge,
+                    fontWeight = FontWeight.SemiBold,
+                    maxLines = 2,
+                    overflow = TextOverflow.Ellipsis,
+                )
+            }
+            dayOfTotal?.let { (day, total) ->
+                Text(
+                    text = stringRes(R.string.calendar_day_of_total, day, total),
+                    style = MaterialTheme.typography.labelSmall,
+                    color = MaterialTheme.colorScheme.primary,
+                    fontWeight = FontWeight.SemiBold,
+                )
+            }
+            view.location?.let {
+                Text(
+                    text = it,
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    maxLines = 1,
+                    overflow = TextOverflow.Ellipsis,
+                )
+            }
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarEmptyState.kt

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+
+/**
+ * Shared empty-state layout used across the calendar surfaces (feed, day, week, collections).
+ * Title is the headline; subtitle gives the user one concrete next step ("tap + to create one").
+ * Keeping all calendar empty states uniform avoids the previous one-line walls of text that
+ * gave the user no guidance about what to do next.
+ */
+@Composable
+fun CalendarEmptyState(
+    title: String,
+    subtitle: String,
+) {
+    Box(
+        modifier = Modifier.fillMaxSize().padding(32.dp),
+        contentAlignment = Alignment.Center,
+    ) {
+        Column(
+            horizontalAlignment = Alignment.CenterHorizontally,
+            verticalArrangement = Arrangement.spacedBy(8.dp),
+        ) {
+            Text(
+                text = title,
+                style = MaterialTheme.typography.titleMedium,
+                fontWeight = FontWeight.SemiBold,
+                color = MaterialTheme.colorScheme.onSurface,
+                textAlign = TextAlign.Center,
+            )
+            Text(
+                text = subtitle,
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                textAlign = TextAlign.Center,
+            )
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarEventListCard.kt

@@ -0,0 +1,237 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.Card
+import androidx.compose.material3.CardDefaults
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
+import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.appointmentView
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.ui.components.MyAsyncImage
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.video.UserCardHeader
+import com.vitorpamplona.quartz.utils.TimeUtils
+import java.time.Instant
+import java.time.ZoneId
+import java.time.format.DateTimeFormatter
+import java.util.Locale
+
+// Thread-safe and hoisted: previously each CalendarDateBadge recompose allocated a new
+// SimpleDateFormat, which (a) is not thread-safe and (b) created 500 allocations while scrolling.
+private val MonthShortFormatter: DateTimeFormatter =
+    DateTimeFormatter.ofPattern("MMM", Locale.getDefault())
+
+@Composable
+fun CalendarEventListCard(
+    note: Note,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+    modifier: Modifier = Modifier,
+) {
+    val view = note.appointmentView() ?: return
+    val range = remember(note.idHex) { formatCalendarRange(note) }
+    val context = LocalContext.current
+    val relative = remember(note.idHex, view.startSeconds) { relativeTimeLabel(context, view, TimeUtils.now()) }
+    val event = note.event ?: return
+    val detailRoute =
+        remember(event.id) {
+            val addr =
+                (event as? com.vitorpamplona.quartz.nip01Core.core.BaseAddressableEvent)?.address()
+            addr?.let { Route.CalendarEventDetail(it) } ?: Route.Note(note.idHex)
+        }
+
+    Card(
+        modifier =
+            modifier
+                .fillMaxWidth()
+                .padding(horizontal = 12.dp, vertical = 6.dp)
+                .clickable { nav.nav(detailRoute) },
+        shape = RoundedCornerShape(14.dp),
+        colors = CardDefaults.elevatedCardColors(),
+        elevation = CardDefaults.elevatedCardElevation(defaultElevation = 2.dp),
+    ) {
+        // Author header matches the picture-feed / shorts card shape: avatar + display name +
+        // time-ago at the top of every social card in the app. Without this, calendar cards
+        // looked alien next to the rest of the feed.
+        UserCardHeader(
+            baseNote = note,
+            accountViewModel = accountViewModel,
+            nav = nav,
+            // Hide the "posted N ago" timestamp — would be visually identical to the event's
+            // own start time below and confuse users into reading the publication date as the
+            // event date.
+            showTimeAgo = false,
+        )
+
+        Row(
+            modifier = Modifier.padding(start = 12.dp, end = 12.dp, bottom = 12.dp),
+            verticalAlignment = Alignment.Top,
+        ) {
+            CalendarDateBadge(view.startSeconds)
+
+            Spacer(modifier = Modifier.size(12.dp))
+
+            Column(
+                modifier = Modifier.fillMaxWidth(),
+                verticalArrangement = Arrangement.spacedBy(4.dp),
+            ) {
+                view.title?.let {
+                    Text(
+                        text = it,
+                        style = MaterialTheme.typography.titleMedium,
+                        fontWeight = FontWeight.SemiBold,
+                        maxLines = 2,
+                        overflow = TextOverflow.Ellipsis,
+                    )
+                }
+                range?.let {
+                    Text(
+                        text = it,
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.primary,
+                        maxLines = 2,
+                        overflow = TextOverflow.Ellipsis,
+                    )
+                }
+                relative?.let {
+                    Text(
+                        text = it,
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        maxLines = 1,
+                        overflow = TextOverflow.Ellipsis,
+                    )
+                }
+                view.location?.let {
+                    Row(verticalAlignment = Alignment.CenterVertically) {
+                        Icon(
+                            symbol = MaterialSymbols.LocationOn,
+                            contentDescription = null,
+                            modifier = Modifier.size(14.dp),
+                            tint = MaterialTheme.colorScheme.onSurfaceVariant,
+                        )
+                        Spacer(modifier = Modifier.size(4.dp))
+                        Text(
+                            text = it,
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant,
+                            maxLines = 1,
+                            overflow = TextOverflow.Ellipsis,
+                        )
+                    }
+                }
+                val image = view.image
+                val summary = view.summary
+                if (!image.isNullOrBlank()) {
+                    Spacer(modifier = Modifier.size(4.dp))
+                    MyAsyncImage(
+                        imageUrl = image,
+                        contentDescription = view.title,
+                        contentScale = ContentScale.Crop,
+                        mainImageModifier = Modifier.fillMaxWidth().height(120.dp),
+                        loadedImageModifier = Modifier,
+                        accountViewModel = accountViewModel,
+                        onLoadingBackground = { Box(modifier = Modifier.fillMaxWidth().height(120.dp)) },
+                        onError = { Box(modifier = Modifier.fillMaxWidth().height(120.dp)) },
+                    )
+                }
+                if (!summary.isNullOrBlank() && image.isNullOrBlank()) {
+                    Text(
+                        text = summary,
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        maxLines = 2,
+                        overflow = TextOverflow.Ellipsis,
+                    )
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun CalendarDateBadge(startSeconds: Long?) {
+    if (startSeconds == null) {
+        Box(
+            modifier = Modifier.size(width = 52.dp, height = 60.dp),
+            contentAlignment = Alignment.Center,
+        ) {
+            Icon(
+                symbol = MaterialSymbols.CalendarMonth,
+                contentDescription = null,
+                modifier = Modifier.size(28.dp),
+                tint = MaterialTheme.colorScheme.primary,
+            )
+        }
+        return
+    }
+
+    val localDate =
+        remember(startSeconds) {
+            Instant.ofEpochSecond(startSeconds).atZone(ZoneId.systemDefault()).toLocalDate()
+        }
+    val day = localDate.dayOfMonth.toString()
+    val month = remember(localDate) { MonthShortFormatter.format(localDate).uppercase() }
+
+    Column(
+        modifier = Modifier.size(width = 52.dp, height = 60.dp),
+        horizontalAlignment = Alignment.CenterHorizontally,
+        verticalArrangement = Arrangement.Center,
+    ) {
+        Text(
+            text = month,
+            style = MaterialTheme.typography.labelSmall,
+            color = MaterialTheme.colorScheme.primary,
+            fontWeight = FontWeight.SemiBold,
+        )
+        Text(
+            text = day,
+            style = MaterialTheme.typography.headlineSmall,
+            color = MaterialTheme.colorScheme.onSurface,
+            fontWeight = FontWeight.Bold,
+        )
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarFeedView.kt

@@ -0,0 +1,201 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.lazy.rememberLazyListState
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.derivedStateOf
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.calendarEndSeconds
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.calendarStartSeconds
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedContentState
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedState
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.ui.feeds.RefresheableBox
+import com.vitorpamplona.amethyst.ui.feeds.WatchScrollToTop
+import com.vitorpamplona.amethyst.ui.layouts.rememberFeedContentPadding
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.amethyst.ui.theme.FeedPadding
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+@Composable
+fun CalendarFeedView(
+    feedState: FeedContentState,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+    filterAddresses: Set<com.vitorpamplona.quartz.nip01Core.core.Address>? = null,
+) {
+    RefresheableBox(feedState, true) {
+        val state by feedState.feedContent.collectAsStateWithLifecycle()
+
+        when (val s = state) {
+            is FeedState.Loaded -> CalendarFeedLoadedBody(s, feedState, accountViewModel, nav, filterAddresses)
+            is FeedState.Empty -> CalendarFeedEmpty()
+            is FeedState.Loading -> Box(modifier = Modifier.fillMaxSize())
+            is FeedState.FeedError -> CalendarFeedError(s)
+        }
+    }
+}
+
+@Composable
+private fun CalendarFeedLoadedBody(
+    loaded: FeedState.Loaded,
+    feedState: FeedContentState,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+    filterAddresses: Set<com.vitorpamplona.quartz.nip01Core.core.Address>?,
+) {
+    val items by loaded.feed.collectAsStateWithLifecycle()
+
+    val split by remember(filterAddresses) {
+        derivedStateOf {
+            partitionUpcomingPast(items.list.applyCalendarFilter(filterAddresses))
+        }
+    }
+
+    // Without this the top-bar filter switch fires `sendToTop()`, but the LazyColumn never hears
+    // it — so the scroll position from the previous filter (e.g. mid-way through a tiny People
+    // List) is preserved when the user flips back to Global, leaving the user staring at the
+    // past-events section of a 100-item feed instead of the top.
+    val listState = rememberLazyListState()
+    WatchScrollToTop(feedState, listState)
+
+    LazyColumn(
+        state = listState,
+        contentPadding = rememberFeedContentPadding(FeedPadding),
+        modifier = Modifier.fillMaxSize(),
+    ) {
+        if (split.upcoming.isNotEmpty()) {
+            item(key = "section-upcoming") {
+                SectionHeader(stringRes(R.string.calendar_section_upcoming))
+            }
+            items(split.upcoming, key = { it.idHex }) { note ->
+                CalendarEventListCard(note, accountViewModel, nav)
+            }
+        }
+
+        if (split.past.isNotEmpty()) {
+            item(key = "section-past") {
+                if (split.upcoming.isNotEmpty()) {
+                    HorizontalDivider(modifier = Modifier.padding(vertical = 8.dp))
+                }
+                SectionHeader(stringRes(R.string.calendar_section_past))
+            }
+            items(split.past, key = { it.idHex }) { note ->
+                CalendarEventListCard(note, accountViewModel, nav)
+            }
+        }
+    }
+}
+
+@Composable
+private fun SectionHeader(text: String) {
+    Text(
+        text = text,
+        style = MaterialTheme.typography.titleSmall,
+        fontWeight = FontWeight.Bold,
+        color = MaterialTheme.colorScheme.primary,
+        modifier = Modifier.padding(start = 16.dp, top = 14.dp, bottom = 6.dp),
+    )
+}
+
+@Composable
+private fun CalendarFeedEmpty() {
+    CalendarEmptyState(
+        title = stringRes(R.string.calendar_empty_feed_title),
+        subtitle = stringRes(R.string.calendar_empty_feed_subtitle),
+    )
+}
+
+@Composable
+private fun CalendarFeedError(state: FeedState.FeedError) {
+    Box(
+        modifier = Modifier.fillMaxSize().padding(32.dp),
+        contentAlignment = Alignment.Center,
+    ) {
+        Text(
+            text = state.errorMessage,
+            style = MaterialTheme.typography.bodyMedium,
+            color = MaterialTheme.colorScheme.error,
+        )
+    }
+}
+
+data class UpcomingPastSplit(
+    val upcoming: List<Note>,
+    val past: List<Note>,
+)
+
+/**
+ * Returns only notes whose appointment address is in [filterAddresses]. Pass null to skip
+ * filtering (the common path when "All" is selected). Lives here as a shared helper so each
+ * view body can keep its own collection logic and just opt-into the filter via one call.
+ */
+fun List<Note>.applyCalendarFilter(filterAddresses: Set<com.vitorpamplona.quartz.nip01Core.core.Address>?): List<Note> {
+    if (filterAddresses == null) return this
+    return filter { note ->
+        val addr =
+            (note.event as? com.vitorpamplona.quartz.nip01Core.core.BaseAddressableEvent)?.address()
+        addr != null && addr in filterAddresses
+    }
+}
+
+/**
+ * [nowSeconds] is taken as a parameter (rather than reading `TimeUtils.now()` internally) so the
+ * split can be unit-tested deterministically and so callers that already snapshot `now` for a
+ * sort don't read the clock twice.
+ */
+fun partitionUpcomingPast(
+    items: List<Note>,
+    nowSeconds: Long = TimeUtils.now(),
+): UpcomingPastSplit {
+    val upcoming = mutableListOf<Note>()
+    val past = mutableListOf<Note>()
+    items.forEach {
+        val s = it.calendarStartSeconds() ?: return@forEach
+        // An event that started yesterday but ends tomorrow is "happening now", not over.
+        // Fall back to start when end is missing so the legacy single-instant behaviour is kept.
+        val effectiveEnd = it.calendarEndSeconds() ?: s
+        if (effectiveEnd >= nowSeconds) {
+            upcoming.add(it)
+        } else {
+            past.add(it)
+        }
+    }
+    return UpcomingPastSplit(upcoming, past)
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarFilterChip.kt

@@ -0,0 +1,206 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material3.AssistChip
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.ModalBottomSheet
+import androidx.compose.material3.RadioButton
+import androidx.compose.material3.Text
+import androidx.compose.material3.rememberModalBottomSheetState
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.produceState
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+
+/**
+ * Top-bar affordance that scopes the appointments feed to a single kind-31924 calendar's
+ * member set. Selecting "All" clears the filter.
+ *
+ * Filter state lives on the screen (passed as [selectedDTag] / [onSelect]) so it survives
+ * configuration changes via rememberSaveable but doesn't persist across launches — keeping a
+ * filter sticky between sessions would surprise a user who set it once and forgot. The filter
+ * is applied client-side after the feed loads, so changing it doesn't trigger a relay refetch.
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun CalendarFilterChip(
+    selectedDTag: String?,
+    onSelect: (String?) -> Unit,
+    accountViewModel: AccountViewModel,
+) {
+    val myPubKey = accountViewModel.userProfile().pubkeyHex
+    val ownCalendars by produceState<List<CalendarEvent>>(initialValue = ownCalendars(myPubKey), myPubKey) {
+        LocalCache.live.newEventBundles.collect {
+            value = ownCalendars(myPubKey)
+        }
+    }
+    val selected = ownCalendars.firstOrNull { it.dTag() == selectedDTag }
+    val label =
+        selected?.title()?.takeIf { it.isNotBlank() }
+            ?: stringRes(R.string.calendar_filter_all)
+
+    var showSheet by remember { mutableStateOf(false) }
+
+    AssistChip(
+        onClick = { showSheet = true },
+        label = {
+            Text(text = label, maxLines = 1, overflow = TextOverflow.Ellipsis)
+        },
+    )
+
+    if (showSheet) {
+        ModalBottomSheet(
+            onDismissRequest = { showSheet = false },
+            sheetState = rememberModalBottomSheetState(skipPartiallyExpanded = true),
+        ) {
+            Column(
+                modifier = Modifier.fillMaxWidth().padding(horizontal = 16.dp, vertical = 8.dp),
+                verticalArrangement = Arrangement.spacedBy(4.dp),
+            ) {
+                Text(
+                    text = stringRes(R.string.calendar_filter_sheet_title),
+                    style = MaterialTheme.typography.titleMedium,
+                    fontWeight = FontWeight.SemiBold,
+                )
+                FilterChoiceRow(
+                    title = stringRes(R.string.calendar_filter_all),
+                    isSelected = selectedDTag == null,
+                    onClick = {
+                        onSelect(null)
+                        showSheet = false
+                    },
+                )
+                if (ownCalendars.isEmpty()) {
+                    Box(
+                        modifier = Modifier.fillMaxWidth().padding(vertical = 16.dp),
+                        contentAlignment = Alignment.Center,
+                    ) {
+                        Text(
+                            text = stringRes(R.string.calendar_filter_no_calendars),
+                            style = MaterialTheme.typography.bodyMedium,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        )
+                    }
+                } else {
+                    LazyColumn(modifier = Modifier.fillMaxWidth()) {
+                        items(ownCalendars, key = { it.dTag() }) { calendar ->
+                            FilterChoiceRow(
+                                title = calendar.title() ?: stringRes(R.string.calendar_untitled),
+                                isSelected = selectedDTag == calendar.dTag(),
+                                onClick = {
+                                    onSelect(calendar.dTag())
+                                    showSheet = false
+                                },
+                            )
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun FilterChoiceRow(
+    title: String,
+    isSelected: Boolean,
+    onClick: () -> Unit,
+) {
+    Row(
+        modifier =
+            Modifier
+                .fillMaxWidth()
+                .clickable(onClick = onClick)
+                .padding(vertical = 8.dp),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        RadioButton(selected = isSelected, onClick = onClick)
+        Text(
+            text = title,
+            style = MaterialTheme.typography.bodyLarge,
+            modifier = Modifier.padding(start = 4.dp),
+            maxLines = 1,
+            overflow = TextOverflow.Ellipsis,
+        )
+    }
+}
+
+private fun ownCalendars(myPubKey: String): List<CalendarEvent> =
+    LocalCache.addressables
+        .filterIntoSet { _, note ->
+            val e = note.event
+            e is CalendarEvent && e.pubKey == myPubKey
+        }.mapNotNull { it.event as? CalendarEvent }
+        .sortedBy { it.title()?.lowercase() ?: "" }
+
+/**
+ * Resolves the selected calendar's member address set, or null when no filter is set. Returned
+ * set is suitable for `.filter { it.calendarAddress() in filter }` membership checks on the
+ * notes the feed views render.
+ */
+@Composable
+fun rememberCalendarFilterAddresses(
+    selectedDTag: String?,
+    accountViewModel: AccountViewModel,
+): Set<Address>? {
+    if (selectedDTag == null) return null
+    val myPubKey = accountViewModel.userProfile().pubkeyHex
+    val addr = remember(selectedDTag, myPubKey) { Address(CalendarEvent.KIND, myPubKey, selectedDTag) }
+    val state by produceState<Set<Address>?>(initialValue = null, addr) {
+        // Re-evaluate on relay-driven changes — when the user edits the calendar elsewhere, the
+        // member set updates here without leaving the screen.
+        value = lookupMembers(addr)
+        LocalCache.live.newEventBundles.collect {
+            value = lookupMembers(addr)
+        }
+    }
+    return state
+}
+
+private fun lookupMembers(addr: Address): Set<Address> =
+    (LocalCache.addressables.get(addr)?.event as? CalendarEvent)
+        ?.calendarEventAddresses()
+        ?.toSet()
+        ?: emptySet()

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarMonthView.kt

@@ -0,0 +1,377 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.border
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.derivedStateOf
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.pluralStringResource
+import androidx.compose.ui.semantics.Role
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.MONTH_GRID_MAX_LANES
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.MonthGridBarSegment
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.computeMonthGridBars
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.groupByDayKeyExpanded
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedContentState
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedState
+import com.vitorpamplona.amethyst.ui.layouts.rememberFeedContentPadding
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.amethyst.ui.theme.FeedPadding
+import java.time.LocalDate
+import java.time.YearMonth
+import java.time.ZoneId
+
+@Composable
+fun CalendarMonthView(
+    feedState: FeedContentState,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+    filterAddresses: Set<com.vitorpamplona.quartz.nip01Core.core.Address>? = null,
+) {
+    val state by feedState.feedContent.collectAsStateWithLifecycle()
+    val notes =
+        when (val s = state) {
+            is FeedState.Loaded ->
+                s.feed
+                    .collectAsStateWithLifecycle()
+                    .value.list
+                    .applyCalendarFilter(filterAddresses)
+            else -> emptyList()
+        }
+
+    val today = remember { LocalDate.now() }
+    // YearMonth is not Parcelable/auto-saveable; persist the two ints and rebuild on each read.
+    var visibleYear by rememberSaveable { mutableStateOf(today.year) }
+    var visibleMonthValue by rememberSaveable { mutableStateOf(today.monthValue) }
+    val visibleMonth = YearMonth.of(visibleYear, visibleMonthValue)
+
+    fun setVisibleMonth(ym: YearMonth) {
+        visibleYear = ym.year
+        visibleMonthValue = ym.monthValue
+    }
+
+    val eventsByDay by remember(notes) { derivedStateOf { groupByDayKeyExpanded(notes) } }
+    val barsByDay by remember(notes) { derivedStateOf { computeMonthGridBars(notes) } }
+
+    var selectedDayKey by rememberSaveable { mutableStateOf<Long?>(null) }
+
+    val selectedEvents = selectedDayKey?.let { eventsByDay[it] }.orEmpty()
+
+    // Single LazyColumn — nav header + weekday header + grid scroll together with the
+    // disappearing top bar so the grid doesn't stay pinned mid-screen when the bar collapses.
+    LazyColumn(
+        contentPadding = rememberFeedContentPadding(FeedPadding),
+        modifier =
+            Modifier
+                .fillMaxSize()
+                .calendarSwipeNavigation(
+                    key = visibleYear to visibleMonthValue,
+                    onSwipeLeft = {
+                        setVisibleMonth(visibleMonth.plusMonths(1))
+                        selectedDayKey = null
+                    },
+                    onSwipeRight = {
+                        setVisibleMonth(visibleMonth.minusMonths(1))
+                        selectedDayKey = null
+                    },
+                ),
+    ) {
+        item(key = "month-nav") {
+            CalendarNavigationHeader(
+                title = formatMonthYear(visibleMonth.year, visibleMonth.monthValue - 1),
+                prevContentDescription = stringRes(R.string.calendar_nav_previous_month),
+                nextContentDescription = stringRes(R.string.calendar_nav_next_month),
+                onPrev = {
+                    setVisibleMonth(visibleMonth.minusMonths(1))
+                    selectedDayKey = null
+                },
+                onNext = {
+                    setVisibleMonth(visibleMonth.plusMonths(1))
+                    selectedDayKey = null
+                },
+                onToday = {
+                    setVisibleMonth(YearMonth.from(LocalDate.now()))
+                    selectedDayKey = null
+                },
+            )
+        }
+
+        item(key = "month-weekday-header") {
+            WeekdayHeader()
+        }
+
+        item(key = "month-grid") {
+            MonthGrid(
+                visibleMonth = visibleMonth,
+                today = today,
+                barsByDay = barsByDay,
+                selectedDayKey = selectedDayKey,
+                onDayClick = { dayKey ->
+                    selectedDayKey = if (selectedDayKey == dayKey) null else dayKey
+                },
+            )
+        }
+
+        item(key = "month-grid-spacer") {
+            Spacer(modifier = Modifier.height(8.dp))
+        }
+
+        if (selectedEvents.isNotEmpty()) {
+            items(selectedEvents, key = { it.idHex }) { note ->
+                CalendarEventListCard(note, accountViewModel, nav)
+            }
+        }
+    }
+}
+
+@Composable
+private fun WeekdayHeader() {
+    Row(modifier = Modifier.fillMaxWidth().padding(horizontal = 4.dp)) {
+        for (i in 0..6) {
+            Text(
+                text = formatShortWeekday(i),
+                style = MaterialTheme.typography.labelSmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.weight(1f).padding(vertical = 4.dp),
+                textAlign = TextAlign.Center,
+                fontWeight = FontWeight.SemiBold,
+            )
+        }
+    }
+}
+
+@Composable
+private fun MonthGrid(
+    visibleMonth: YearMonth,
+    today: LocalDate,
+    barsByDay: Map<Long, List<MonthGridBarSegment>>,
+    selectedDayKey: Long?,
+    onDayClick: (Long) -> Unit,
+) {
+    val firstOfMonth = visibleMonth.atDay(1)
+    // SUNDAY = 7 in DayOfWeek; we want Sunday = 0 to match `formatShortWeekday`.
+    val firstWeekdayIndex = firstOfMonth.dayOfWeek.value % 7
+    val daysInMonth = visibleMonth.lengthOfMonth()
+    val rows = ((firstWeekdayIndex + daysInMonth + 6) / 7)
+    val isCurrentMonth = visibleMonth == YearMonth.from(today)
+
+    Column(modifier = Modifier.fillMaxWidth()) {
+        for (r in 0 until rows) {
+            Row(modifier = Modifier.fillMaxWidth()) {
+                for (c in 0..6) {
+                    val cellIndex = r * 7 + c
+                    val dayNumber = cellIndex - firstWeekdayIndex + 1
+                    if (dayNumber in 1..daysInMonth) {
+                        val date = visibleMonth.atDay(dayNumber)
+                        val dayKey = date.toEpochDay()
+                        val cellBars = barsByDay[dayKey].orEmpty()
+                        val isToday = isCurrentMonth && date == today
+                        val isSelected = selectedDayKey == dayKey
+                        DayCell(
+                            modifier = Modifier.weight(1f),
+                            dayNumber = dayNumber,
+                            isToday = isToday,
+                            isSelected = isSelected,
+                            bars = cellBars,
+                            // Anything past the visible lane cap collapses into a "+N" tail —
+                            // keeps each cell readable when a day has more than three events.
+                            extraEventCount = cellBars.count { it.lane >= MONTH_GRID_MAX_LANES },
+                            isWeekStart = c == 0,
+                            isWeekEnd = c == 6,
+                            // Full date label fed to the screen-reader content description so
+                            // TalkBack reads "Wednesday January 15 2025, 2 events" instead of
+                            // just "15".
+                            dateLabel = formatLongDate(date.atStartOfDay(ZoneId.systemDefault()).toEpochSecond()),
+                            totalEventCount = cellBars.size,
+                            onClick = { onDayClick(dayKey) },
+                        )
+                    } else {
+                        Box(modifier = Modifier.weight(1f).height(MONTH_CELL_HEIGHT))
+                    }
+                }
+            }
+        }
+    }
+}
+
+private val MONTH_CELL_HEIGHT = 72.dp
+
+@Composable
+private fun DayCell(
+    modifier: Modifier,
+    dayNumber: Int,
+    isToday: Boolean,
+    isSelected: Boolean,
+    bars: List<MonthGridBarSegment>,
+    extraEventCount: Int,
+    isWeekStart: Boolean,
+    isWeekEnd: Boolean,
+    dateLabel: String,
+    totalEventCount: Int,
+    onClick: () -> Unit,
+) {
+    val bg =
+        if (isSelected) {
+            MaterialTheme.colorScheme.primaryContainer
+        } else {
+            MaterialTheme.colorScheme.surface
+        }
+
+    val baseDescription =
+        pluralStringResource(R.plurals.calendar_day_a11y_events, totalEventCount, dateLabel, totalEventCount)
+    val todaySuffix = stringRes(R.string.calendar_day_a11y_today_suffix)
+    val selectedSuffix = stringRes(R.string.calendar_day_a11y_selected_suffix)
+    val a11y =
+        buildString {
+            append(baseDescription)
+            if (isToday) append(", ").append(todaySuffix)
+            if (isSelected) append(", ").append(selectedSuffix)
+        }
+
+    Box(
+        modifier =
+            modifier
+                .height(MONTH_CELL_HEIGHT)
+                // Vertical-only padding so adjacent cells in a row touch horizontally — a
+                // multi-day bar that extends from the right edge of one cell to the left edge of
+                // the next visually merges into a single uninterrupted line.
+                .padding(vertical = 2.dp)
+                .background(bg, RoundedCornerShape(8.dp))
+                .border(
+                    width = if (isToday) 1.5.dp else 0.5.dp,
+                    color = if (isToday) MaterialTheme.colorScheme.primary else MaterialTheme.colorScheme.outlineVariant,
+                    shape = RoundedCornerShape(8.dp),
+                ).clickable(role = Role.Button, onClick = onClick)
+                .semantics(mergeDescendants = true) { contentDescription = a11y },
+    ) {
+        Column(
+            modifier = Modifier.fillMaxSize().padding(horizontal = 2.dp, vertical = 4.dp),
+            horizontalAlignment = Alignment.CenterHorizontally,
+        ) {
+            Text(
+                text = dayNumber.toString(),
+                style = MaterialTheme.typography.bodyMedium,
+                fontWeight = if (isToday) FontWeight.Bold else FontWeight.Normal,
+                color =
+                    if (isToday) {
+                        MaterialTheme.colorScheme.primary
+                    } else {
+                        MaterialTheme.colorScheme.onSurface
+                    },
+            )
+            Spacer(modifier = Modifier.height(2.dp))
+            EventBarLanes(
+                bars = bars,
+                extraEventCount = extraEventCount,
+                isWeekStart = isWeekStart,
+                isWeekEnd = isWeekEnd,
+            )
+        }
+    }
+}
+
+/**
+ * Renders up to [MONTH_GRID_MAX_LANES] horizontal bars stacked vertically. Each lane occupies a
+ * fixed height across every cell so a multi-day event sits on the same y-row in every column it
+ * covers — the visual continuity that makes "spans 3 days" readable at a glance.
+ *
+ * The bar is rounded only at the event's start (`isLeftEnd`) and end (`isRightEnd`). On week
+ * boundaries we also round so each row of the grid looks self-contained instead of bleeding into
+ * an unaligned next row.
+ */
+@Composable
+private fun EventBarLanes(
+    bars: List<MonthGridBarSegment>,
+    extraEventCount: Int,
+    isWeekStart: Boolean,
+    isWeekEnd: Boolean,
+) {
+    val barColor = MaterialTheme.colorScheme.primary
+    Column(
+        modifier = Modifier.fillMaxWidth(),
+        verticalArrangement = Arrangement.spacedBy(1.dp),
+    ) {
+        for (i in 0 until MONTH_GRID_MAX_LANES) {
+            val seg = bars.firstOrNull { it.lane == i }
+            if (seg != null) {
+                val roundLeft = seg.isLeftEnd || isWeekStart
+                val roundRight = seg.isRightEnd || isWeekEnd
+                Box(
+                    modifier =
+                        Modifier
+                            .fillMaxWidth()
+                            .height(5.dp)
+                            .background(
+                                color = barColor,
+                                shape =
+                                    RoundedCornerShape(
+                                        topStart = if (roundLeft) 2.dp else 0.dp,
+                                        bottomStart = if (roundLeft) 2.dp else 0.dp,
+                                        topEnd = if (roundRight) 2.dp else 0.dp,
+                                        bottomEnd = if (roundRight) 2.dp else 0.dp,
+                                    ),
+                            ),
+                )
+            } else {
+                Spacer(modifier = Modifier.fillMaxWidth().height(5.dp))
+            }
+        }
+        if (extraEventCount > 0) {
+            Text(
+                text = "+$extraEventCount",
+                style = MaterialTheme.typography.labelSmall,
+                color = barColor,
+                fontWeight = FontWeight.SemiBold,
+            )
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarNavigationHeader.kt

@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.semantics.Role
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
+import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.ui.stringRes
+
+/**
+ * Shared `[◀] title [▶]` header used by month / week / day view bodies. Tapping the title
+ * jumps back to today.
+ */
+@Composable
+fun CalendarNavigationHeader(
+    title: String,
+    prevContentDescription: String,
+    nextContentDescription: String,
+    onPrev: () -> Unit,
+    onNext: () -> Unit,
+    onToday: () -> Unit,
+) {
+    Row(
+        modifier = Modifier.fillMaxWidth().padding(horizontal = 12.dp, vertical = 6.dp),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        IconButton(onClick = onPrev) {
+            Icon(
+                symbol = MaterialSymbols.AutoMirrored.ArrowBack,
+                contentDescription = prevContentDescription,
+                modifier = Modifier.size(20.dp),
+                tint = MaterialTheme.colorScheme.onSurface,
+            )
+        }
+        // Title doubles as the "jump to today" affordance. Adding a TalkBack-only contentDescription
+        // makes that role discoverable for screen-reader users — the bare text alone reads as a
+        // label, not an action.
+        val jumpToToday = stringRes(R.string.calendar_nav_jump_to_today)
+        Text(
+            text = title,
+            style = MaterialTheme.typography.titleLarge,
+            modifier =
+                Modifier
+                    .weight(1f)
+                    .clickable(role = Role.Button, onClickLabel = jumpToToday, onClick = onToday)
+                    .semantics { contentDescription = "$title, $jumpToToday" },
+            textAlign = TextAlign.Center,
+            fontWeight = FontWeight.Bold,
+        )
+        IconButton(onClick = onNext) {
+            Icon(
+                symbol = MaterialSymbols.ChevronRight,
+                contentDescription = nextContentDescription,
+                modifier = Modifier.size(20.dp),
+                tint = MaterialTheme.colorScheme.onSurface,
+            )
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarRelativeTime.kt

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import android.content.Context
+import android.text.format.DateUtils
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.CalendarAppointmentView
+
+/**
+ * Localised "starts in 2 hours" / "started 5 minutes ago" / "Happening now · ends in 2 hours"
+ * label for an appointment. Returns null when the event has no parseable start (nothing to
+ * anchor a relative phrase to).
+ *
+ * Uses [DateUtils.getRelativeTimeSpanString] for the underlying minute/hour/day phrasing — that
+ * helper is locale-aware and ages from "just now" through "in N days" to absolute date for
+ * far-out events. For all-day events we extend the resolution to DAY so we get "tomorrow",
+ * "in 3 days" instead of an hour-precision phrase that would lie about the start moment.
+ *
+ * Ongoing events (start ≤ now ≤ end) get a composite "Happening now · ends in X" so a user
+ * mid-event sees how much time is left rather than the misleading "started X minutes ago" that
+ * DateUtils would produce on its own.
+ */
+fun relativeTimeLabel(
+    context: Context,
+    view: CalendarAppointmentView,
+    nowSeconds: Long,
+): String? {
+    val start = view.startSeconds ?: return null
+    val end = view.endSeconds
+
+    if (end != null && start <= nowSeconds && nowSeconds <= end) {
+        val ongoing = context.getString(R.string.calendar_relative_ongoing)
+        val endsIn =
+            DateUtils
+                .getRelativeTimeSpanString(
+                    end * 1000L,
+                    nowSeconds * 1000L,
+                    if (view.isAllDay) DateUtils.DAY_IN_MILLIS else DateUtils.MINUTE_IN_MILLIS,
+                    DateUtils.FORMAT_ABBREV_RELATIVE,
+                ).toString()
+        return context.getString(R.string.calendar_relative_ongoing_with_end, ongoing, endsIn)
+    }
+
+    val minResolution =
+        if (view.isAllDay) {
+            DateUtils.DAY_IN_MILLIS
+        } else {
+            DateUtils.MINUTE_IN_MILLIS
+        }
+
+    return DateUtils
+        .getRelativeTimeSpanString(
+            start * 1000L,
+            nowSeconds * 1000L,
+            minResolution,
+            DateUtils.FORMAT_ABBREV_RELATIVE,
+        ).toString()
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarReminderSettingsScreen.kt

@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.FilterChip
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Switch
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBar
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableIntStateOf
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
+import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.service.calendar.CalendarReminderPrefs
+import com.vitorpamplona.amethyst.service.calendar.CalendarReminderWorker
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.stringRes
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun CalendarReminderSettingsScreen(nav: INav) {
+    val context = LocalContext.current
+    val prefs = remember { CalendarReminderPrefs(context) }
+    var enabled by remember { mutableStateOf(prefs.isEnabled()) }
+    var leadMinutes by remember { mutableIntStateOf(prefs.leadMinutes()) }
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text(stringRes(R.string.calendar_reminder_settings_title)) },
+                navigationIcon = {
+                    IconButton(onClick = { nav.popBack() }) {
+                        Icon(
+                            symbol = MaterialSymbols.AutoMirrored.ArrowBack,
+                            contentDescription = stringRes(R.string.back),
+                            modifier = Modifier.size(20.dp),
+                            tint = MaterialTheme.colorScheme.onSurface,
+                        )
+                    }
+                },
+            )
+        },
+    ) { pad ->
+        Column(
+            modifier =
+                Modifier
+                    .padding(pad)
+                    .padding(horizontal = 16.dp, vertical = 12.dp),
+            verticalArrangement = Arrangement.spacedBy(12.dp),
+        ) {
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                verticalAlignment = Alignment.CenterVertically,
+            ) {
+                Column(modifier = Modifier.weight(1f)) {
+                    Text(
+                        text = stringRes(R.string.calendar_reminder_settings_enabled_title),
+                        style = MaterialTheme.typography.titleSmall,
+                    )
+                    Text(
+                        text = stringRes(R.string.calendar_reminder_settings_enabled_subtitle),
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                }
+                Switch(
+                    checked = enabled,
+                    onCheckedChange = {
+                        enabled = it
+                        prefs.setEnabled(it)
+                        // Toggling off doesn't cancel the worker — the worker itself short-
+                        // circuits when isEnabled() returns false. Keeping the schedule alive
+                        // means flipping it back on takes effect immediately without needing a
+                        // re-launch via AppModules.
+                        if (it) CalendarReminderWorker.schedule(context)
+                    },
+                )
+            }
+
+            Text(
+                text = stringRes(R.string.calendar_reminder_settings_lead_title),
+                style = MaterialTheme.typography.titleSmall,
+                modifier = Modifier.padding(top = 8.dp),
+            )
+            Text(
+                text = stringRes(R.string.calendar_reminder_settings_lead_subtitle),
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                CalendarReminderPrefs.LEAD_TIME_CHOICES.forEach { choice ->
+                    FilterChip(
+                        selected = choice == leadMinutes,
+                        onClick = {
+                            leadMinutes = choice
+                            prefs.setLeadMinutes(choice)
+                        },
+                        enabled = enabled,
+                        label = {
+                            Text(stringRes(R.string.calendar_reminder_settings_lead_choice, choice))
+                        },
+                    )
+                }
+            }
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarScaffoldPadding.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.layout.padding
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.composed
+import com.vitorpamplona.amethyst.ui.layouts.LocalDisappearingScaffoldPadding
+
+/**
+ * Applies the surrounding [com.vitorpamplona.amethyst.ui.layouts.DisappearingScaffold]'s reserved
+ * top/bottom space as padding. The scaffold places content at y=0 by design — it lets feeds
+ * scroll *behind* the disappearing bar — but the month/week/day views are static-headered grids,
+ * so without this modifier the grid header would render under the top app bar. Outside a
+ * scaffold the local default is zero and the modifier is a no-op.
+ */
+@Composable
+fun Modifier.disappearingScaffoldPadding(): Modifier =
+    composed {
+        val padding = LocalDisappearingScaffoldPadding.current
+        this.padding(padding)
+    }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarSwipeNavigation.kt

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.gestures.detectHorizontalDragGestures
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.input.pointer.pointerInput
+
+/**
+ * Swipe-to-navigate gesture for calendar surfaces. Horizontal drag past the threshold fires
+ * [onSwipeLeft] (next period) or [onSwipeRight] (previous period). The threshold is in pixels
+ * — we accumulate raw drag deltas because [detectHorizontalDragGestures]' final-velocity callback
+ * isn't surfaced here; a positional threshold gives the user predictable, latch-style behaviour
+ * comparable to the previous/next arrows in [CalendarNavigationHeader].
+ *
+ * The `key` lets a host that swaps state (week → next week, day → next day) restart the gesture
+ * detector so a long sequence of partial drags doesn't accumulate across navigations.
+ */
+fun Modifier.calendarSwipeNavigation(
+    key: Any?,
+    onSwipeLeft: () -> Unit,
+    onSwipeRight: () -> Unit,
+    thresholdPx: Float = 120f,
+): Modifier =
+    this.pointerInput(key) {
+        var totalDrag = 0f
+        detectHorizontalDragGestures(
+            onDragStart = { totalDrag = 0f },
+            onDragEnd = {
+                if (totalDrag <= -thresholdPx) {
+                    onSwipeLeft()
+                } else if (totalDrag >= thresholdPx) {
+                    onSwipeRight()
+                }
+                totalDrag = 0f
+            },
+            onDragCancel = { totalDrag = 0f },
+        ) { _, dragAmount ->
+            totalDrag += dragAmount
+        }
+    }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarTimeFormat.kt

@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.appointmentView
+import com.vitorpamplona.amethyst.model.Note
+import java.text.SimpleDateFormat
+import java.util.Calendar
+import java.util.Date
+import java.util.Locale
+
+private val DayMonthFormat = SimpleDateFormat("EEE, MMM d", Locale.getDefault())
+private val FullDateFormat = SimpleDateFormat("EEEE, MMMM d, yyyy", Locale.getDefault())
+private val MonthYearFormat = SimpleDateFormat("MMMM yyyy", Locale.getDefault())
+private val TimeFormat = SimpleDateFormat("h:mm a", Locale.getDefault())
+private val WeekdayShortFormat = SimpleDateFormat("EEE", Locale.getDefault())
+
+fun formatCalendarRange(note: Note): String? {
+    val view = note.appointmentView() ?: return null
+    val start = view.startSeconds ?: return null
+    return if (view.isAllDay) {
+        formatDateRange(start, view.endSeconds)
+    } else {
+        formatTimeRange(start, view.endSeconds)
+    }
+}
+
+private fun formatTimeRange(
+    start: Long,
+    end: Long?,
+): String {
+    val startMs = start * 1000
+    val startStr = "${DayMonthFormat.format(Date(startMs))} · ${TimeFormat.format(Date(startMs))}"
+    if (end == null || end == start) return startStr
+    val endMs = end * 1000
+    return if (isSameDay(startMs, endMs)) {
+        "$startStr – ${TimeFormat.format(Date(endMs))}"
+    } else {
+        "$startStr – ${DayMonthFormat.format(Date(endMs))} · ${TimeFormat.format(Date(endMs))}"
+    }
+}
+
+private fun formatDateRange(
+    start: Long,
+    end: Long?,
+): String {
+    val startStr = DayMonthFormat.format(Date(start * 1000))
+    if (end == null || end == start) return startStr
+    return "$startStr – ${DayMonthFormat.format(Date(end * 1000))}"
+}
+
+fun formatLongDate(unixSeconds: Long): String = FullDateFormat.format(Date(unixSeconds * 1000))
+
+fun formatMonthYear(
+    year: Int,
+    monthZeroBased: Int,
+): String {
+    val cal = Calendar.getInstance()
+    cal.clear()
+    cal.set(year, monthZeroBased, 1)
+    return MonthYearFormat.format(cal.time)
+}
+
+fun formatTimeOfDay(unixSeconds: Long): String = TimeFormat.format(Date(unixSeconds * 1000))
+
+fun formatShortWeekday(weekdayZeroBased: Int): String {
+    val cal = Calendar.getInstance()
+    cal.clear()
+    cal.firstDayOfWeek = Calendar.SUNDAY
+    cal.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY)
+    cal.add(Calendar.DAY_OF_YEAR, weekdayZeroBased)
+    return WeekdayShortFormat.format(cal.time)
+}
+
+private fun isSameDay(
+    aMs: Long,
+    bMs: Long,
+): Boolean {
+    val ca = Calendar.getInstance().apply { timeInMillis = aMs }
+    val cb = Calendar.getInstance().apply { timeInMillis = bMs }
+    return ca.get(Calendar.YEAR) == cb.get(Calendar.YEAR) &&
+        ca.get(Calendar.DAY_OF_YEAR) == cb.get(Calendar.DAY_OF_YEAR)
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarWeekView.kt

@@ -0,0 +1,277 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.border
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.derivedStateOf
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.pluralStringResource
+import androidx.compose.ui.semantics.Role
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.groupByDayKeyExpanded
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedContentState
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedState
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.ui.layouts.rememberFeedContentPadding
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.amethyst.ui.theme.FeedPadding
+import java.time.LocalDate
+import java.time.ZoneId
+
+@Composable
+fun CalendarWeekView(
+    feedState: FeedContentState,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+    filterAddresses: Set<com.vitorpamplona.quartz.nip01Core.core.Address>? = null,
+) {
+    val state by feedState.feedContent.collectAsStateWithLifecycle()
+    val notes =
+        when (val s = state) {
+            is FeedState.Loaded ->
+                s.feed
+                    .collectAsStateWithLifecycle()
+                    .value.list
+                    .applyCalendarFilter(filterAddresses)
+            else -> emptyList()
+        }
+
+    val today = remember { LocalDate.now() }
+    // Persist the week-start as an epoch-day Long (auto-saveable), reconstruct LocalDate on use.
+    var weekStartEpochDay by rememberSaveable {
+        mutableStateOf(startOfWeek(today).toEpochDay())
+    }
+    val weekStart = LocalDate.ofEpochDay(weekStartEpochDay)
+
+    var selectedDayIndex by rememberSaveable { mutableStateOf(0) }
+
+    val eventsByDay by remember(notes) { derivedStateOf { groupByDayKeyExpanded(notes) } }
+
+    val selectedDate = weekStart.plusDays(selectedDayIndex.toLong())
+    val dayNotes = eventsByDay[selectedDate.toEpochDay()].orEmpty()
+
+    // Single LazyColumn containing nav + strip + day-summary + events so the whole stack
+    // scrolls together with the [DisappearingScaffold]'s top bar. The previous Column-with-
+    // disappearingScaffoldPadding kept the strip pinned at a fixed offset, so when the top bar
+    // collapsed on scroll the strip stayed put and left a visual gap.
+    LazyColumn(
+        contentPadding = rememberFeedContentPadding(FeedPadding),
+        modifier =
+            Modifier
+                .fillMaxSize()
+                .calendarSwipeNavigation(
+                    key = weekStartEpochDay,
+                    onSwipeLeft = {
+                        weekStartEpochDay = weekStart.plusWeeks(1).toEpochDay()
+                        selectedDayIndex = 0
+                    },
+                    onSwipeRight = {
+                        weekStartEpochDay = weekStart.minusWeeks(1).toEpochDay()
+                        selectedDayIndex = 0
+                    },
+                ),
+    ) {
+        item(key = "week-nav") {
+            CalendarNavigationHeader(
+                title = formatMonthYear(weekStart.year, weekStart.monthValue - 1),
+                prevContentDescription = stringRes(R.string.calendar_nav_previous_week),
+                nextContentDescription = stringRes(R.string.calendar_nav_next_week),
+                onPrev = {
+                    weekStartEpochDay = weekStart.minusWeeks(1).toEpochDay()
+                    selectedDayIndex = 0
+                },
+                onNext = {
+                    weekStartEpochDay = weekStart.plusWeeks(1).toEpochDay()
+                    selectedDayIndex = 0
+                },
+                onToday = {
+                    weekStartEpochDay = startOfWeek(LocalDate.now()).toEpochDay()
+                    selectedDayIndex = 0
+                },
+            )
+        }
+
+        item(key = "week-strip") {
+            WeekStrip(
+                weekStart = weekStart,
+                today = today,
+                selectedIndex = selectedDayIndex,
+                eventsByDay = eventsByDay,
+                onSelect = { selectedDayIndex = it },
+            )
+        }
+
+        item(key = "week-spacer") {
+            Spacer(modifier = Modifier.height(8.dp))
+        }
+
+        item(key = "week-day-summary") {
+            DaySummaryHeader(selectedDate)
+        }
+
+        if (dayNotes.isEmpty()) {
+            item(key = "week-empty") {
+                CalendarEmptyState(
+                    title = stringRes(R.string.calendar_empty_week_title),
+                    subtitle = stringRes(R.string.calendar_empty_week_subtitle),
+                )
+            }
+        } else {
+            items(dayNotes, key = { it.idHex }) { note ->
+                CalendarEventListCard(note, accountViewModel, nav)
+            }
+        }
+    }
+}
+
+@Composable
+private fun WeekStrip(
+    weekStart: LocalDate,
+    today: LocalDate,
+    selectedIndex: Int,
+    eventsByDay: Map<Long, List<Note>>,
+    onSelect: (Int) -> Unit,
+) {
+    Row(
+        modifier = Modifier.fillMaxWidth().padding(horizontal = 4.dp),
+    ) {
+        for (i in 0..6) {
+            val date = weekStart.plusDays(i.toLong())
+            val count = eventsByDay[date.toEpochDay()]?.size ?: 0
+            val isToday = date == today
+            val isSelected = i == selectedIndex
+
+            val bg =
+                when {
+                    isSelected -> MaterialTheme.colorScheme.primary
+                    isToday -> MaterialTheme.colorScheme.primaryContainer
+                    else -> MaterialTheme.colorScheme.surface
+                }
+            val fg =
+                when {
+                    isSelected -> MaterialTheme.colorScheme.onPrimary
+                    isToday -> MaterialTheme.colorScheme.onPrimaryContainer
+                    else -> MaterialTheme.colorScheme.onSurface
+                }
+
+            val dateLabel = formatLongDate(date.atStartOfDay(ZoneId.systemDefault()).toEpochSecond())
+            val baseA11y = pluralStringResource(R.plurals.calendar_day_a11y_events, count, dateLabel, count)
+            val todaySuffix = stringRes(R.string.calendar_day_a11y_today_suffix)
+            val selectedSuffix = stringRes(R.string.calendar_day_a11y_selected_suffix)
+            val a11y =
+                buildString {
+                    append(baseA11y)
+                    if (isToday) append(", ").append(todaySuffix)
+                    if (isSelected) append(", ").append(selectedSuffix)
+                }
+
+            Column(
+                modifier =
+                    Modifier
+                        .weight(1f)
+                        .padding(3.dp)
+                        .background(bg, RoundedCornerShape(10.dp))
+                        .border(
+                            width = 0.5.dp,
+                            color = MaterialTheme.colorScheme.outlineVariant,
+                            shape = RoundedCornerShape(10.dp),
+                        ).clickable(role = Role.Tab) { onSelect(i) }
+                        .padding(vertical = 6.dp)
+                        .semantics(mergeDescendants = true) { contentDescription = a11y },
+                horizontalAlignment = Alignment.CenterHorizontally,
+            ) {
+                Text(
+                    text = formatShortWeekday(i),
+                    style = MaterialTheme.typography.labelSmall,
+                    color = fg,
+                    fontWeight = FontWeight.SemiBold,
+                )
+                Text(
+                    text = date.dayOfMonth.toString(),
+                    style = MaterialTheme.typography.titleMedium,
+                    color = fg,
+                    fontWeight = FontWeight.Bold,
+                )
+                if (count > 0) {
+                    Text(
+                        text = if (count > 9) "9+" else count.toString(),
+                        style = MaterialTheme.typography.labelSmall,
+                        color = fg,
+                        maxLines = 1,
+                        overflow = TextOverflow.Clip,
+                    )
+                } else {
+                    Spacer(modifier = Modifier.height(14.dp))
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun DaySummaryHeader(date: LocalDate) {
+    Text(
+        text = formatLongDate(date.atStartOfDay(ZoneId.systemDefault()).toEpochSecond()),
+        style = MaterialTheme.typography.titleSmall,
+        fontWeight = FontWeight.Bold,
+        color = MaterialTheme.colorScheme.primary,
+        modifier = Modifier.padding(start = 16.dp, top = 8.dp, bottom = 4.dp),
+    )
+}
+
+/**
+ * Returns the Sunday on or before [date]. DST-safe because [LocalDate] arithmetic ignores zones.
+ * `DayOfWeek.SUNDAY.value` is 7 in java.time, so `% 7` collapses Sunday → 0 with the rest of the
+ * week following in order.
+ */
+private fun startOfWeek(date: LocalDate): LocalDate {
+    val daysFromSunday = date.dayOfWeek.value % 7
+    return date.minusDays(daysFromSunday.toLong())
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarsScreen.kt

@@ -0,0 +1,136 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedContentState
+import com.vitorpamplona.amethyst.ui.feeds.WatchLifecycleAndUpdateModel
+import com.vitorpamplona.amethyst.ui.layouts.DisappearingScaffold
+import com.vitorpamplona.amethyst.ui.navigation.bottombars.AppBottomBar
+import com.vitorpamplona.amethyst.ui.navigation.bottombars.FabBottomBarPadded
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.CalendarsFilterAssemblerSubscription
+
+@Composable
+fun CalendarsScreen(
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    CalendarsScreen(
+        feedState = accountViewModel.feedStates.calendarAppointmentsFeed,
+        accountViewModel = accountViewModel,
+        nav = nav,
+    )
+}
+
+@Composable
+fun CalendarsScreen(
+    feedState: FeedContentState,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    WatchLifecycleAndUpdateModel(feedState)
+    WatchAccountForCalendarsScreen(feedState, accountViewModel)
+    CalendarsFilterAssemblerSubscription(accountViewModel)
+
+    var viewMode by rememberSaveable { mutableStateOf(CalendarsViewMode.FEED) }
+    var filterDTag by rememberSaveable { mutableStateOf<String?>(null) }
+    // Resolve the selected calendar's member addresses (or null when "All"). Plumbed into each
+    // view so the membership filter is applied client-side after the feed loads — changing the
+    // filter doesn't trigger a relay refetch.
+    val filterAddresses = rememberCalendarFilterAddresses(filterDTag, accountViewModel)
+
+    DisappearingScaffold(
+        isInvertedLayout = false,
+        topBar = {
+            CalendarsTopBar(
+                viewMode = viewMode,
+                onViewModeChange = { viewMode = it },
+                accountViewModel = accountViewModel,
+                nav = nav,
+                trailing = {
+                    CalendarFilterChip(
+                        selectedDTag = filterDTag,
+                        onSelect = { filterDTag = it },
+                        accountViewModel = accountViewModel,
+                    )
+                },
+            )
+        },
+        bottomBar = {
+            AppBottomBar(Route.Calendars, nav, accountViewModel) { route ->
+                if (route == Route.Calendars) {
+                    feedState.sendToTop()
+                } else {
+                    nav.navBottomBar(route)
+                }
+            }
+        },
+        floatingButton = {
+            FabBottomBarPadded(nav) {
+                NewCalendarButton(nav)
+            }
+        },
+        accountViewModel = accountViewModel,
+    ) {
+        Box(modifier = Modifier.fillMaxSize()) {
+            Column(modifier = Modifier.fillMaxSize()) {
+                when (viewMode) {
+                    CalendarsViewMode.FEED ->
+                        CalendarFeedView(feedState, accountViewModel, nav, filterAddresses)
+                    CalendarsViewMode.MONTH ->
+                        CalendarMonthView(feedState, accountViewModel, nav, filterAddresses)
+                    CalendarsViewMode.WEEK ->
+                        CalendarWeekView(feedState, accountViewModel, nav, filterAddresses)
+                    CalendarsViewMode.DAY ->
+                        CalendarDayView(feedState, accountViewModel, nav, filterAddresses)
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun WatchAccountForCalendarsScreen(
+    feedState: FeedContentState,
+    accountViewModel: AccountViewModel,
+) {
+    val listState by accountViewModel.account.liveCalendarsFollowLists.collectAsStateWithLifecycle()
+    val hiddenUsers by
+        accountViewModel.account.hiddenUsers.flow
+            .collectAsStateWithLifecycle()
+
+    LaunchedEffect(accountViewModel, listState, hiddenUsers) {
+        feedState.checkKeysInvalidateDataAndSendToTop()
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarsTopBar.kt

@@ -0,0 +1,132 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.foundation.horizontalScroll
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.material3.FilterChip
+import androidx.compose.material3.FilterChipDefaults
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.model.TopFilter
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.topbars.FeedFilterSpinner
+import com.vitorpamplona.amethyst.ui.navigation.topbars.UserDrawerSearchTopBar
+import com.vitorpamplona.amethyst.ui.screen.FeedDefinition
+import com.vitorpamplona.amethyst.ui.screen.TopNavFilterState
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+
+@Composable
+fun CalendarsTopBar(
+    viewMode: CalendarsViewMode,
+    onViewModeChange: (CalendarsViewMode) -> Unit,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+    // Optional trailing slot for screen-specific extras (the calendar-membership filter
+    // currently lives here). Kept generic so future controls can plug in the same way without
+    // top-bar surgery.
+    trailing: (@Composable () -> Unit)? = null,
+) {
+    Column {
+        UserDrawerSearchTopBar(accountViewModel, nav) {
+            val list by accountViewModel.account.settings.defaultCalendarsFollowList
+                .collectAsStateWithLifecycle()
+
+            CalendarsTopNavFilterBar(
+                followListsModel = accountViewModel.feedStates.feedListOptions,
+                listName = list,
+                accountViewModel = accountViewModel,
+                onChange = accountViewModel.account.settings::changeDefaultCalendarsFollowList,
+            )
+        }
+
+        Row(
+            modifier = Modifier.fillMaxWidth().padding(horizontal = 8.dp),
+            verticalAlignment = androidx.compose.ui.Alignment.CenterVertically,
+        ) {
+            CalendarsViewModeTabs(
+                current = viewMode,
+                onChange = onViewModeChange,
+                modifier = Modifier.weight(1f),
+            )
+            trailing?.invoke()
+        }
+    }
+}
+
+@Composable
+private fun CalendarsTopNavFilterBar(
+    followListsModel: TopNavFilterState,
+    listName: TopFilter,
+    accountViewModel: AccountViewModel,
+    onChange: (FeedDefinition) -> Unit,
+) {
+    val allLists by followListsModel.kind3GlobalPeopleRoutes.collectAsStateWithLifecycle()
+
+    FeedFilterSpinner(
+        placeholderCode = listName,
+        explainer = stringRes(R.string.select_list_to_filter),
+        options = allLists,
+        onSelect = onChange,
+        accountViewModel = accountViewModel,
+    )
+}
+
+@Composable
+private fun CalendarsViewModeTabs(
+    current: CalendarsViewMode,
+    onChange: (CalendarsViewMode) -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    Row(
+        modifier =
+            modifier
+                .horizontalScroll(rememberScrollState())
+                .padding(vertical = 4.dp),
+    ) {
+        CalendarsViewMode.entries.forEach { mode ->
+            FilterChip(
+                selected = mode == current,
+                onClick = { onChange(mode) },
+                label = {
+                    Text(
+                        text = stringRes(mode.labelRes),
+                        style = MaterialTheme.typography.labelLarge,
+                    )
+                },
+                modifier = Modifier.padding(end = 6.dp),
+                colors = FilterChipDefaults.filterChipColors(),
+                shape = MaterialTheme.shapes.small,
+            )
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/CalendarsViewMode.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.annotation.StringRes
+import com.vitorpamplona.amethyst.R
+
+/**
+ * Lenses on the same appointment timeline. Calendar *collections* (kind 31924) live on their
+ * own screen ([CalendarCollectionsScreen]) since they're a sibling feed, not a different view
+ * of the appointment data.
+ */
+enum class CalendarsViewMode(
+    @StringRes val labelRes: Int,
+) {
+    FEED(R.string.calendar_view_feed),
+    MONTH(R.string.calendar_view_month),
+    WEEK(R.string.calendar_view_week),
+    DAY(R.string.calendar_view_day),
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/IcsShare.kt

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import android.content.Context
+import android.content.Intent
+import androidx.core.content.FileProvider
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.ui.stringRes
+import java.io.File
+
+/**
+ * Writes [content] to a `.ics` file in the app's cache dir and opens the system share sheet so
+ * the user can hand the file to a calendar app, email client, file manager, etc.
+ *
+ * The file lives in `cacheDir/calendar/` — covered by the existing `<cache-path>` entry in
+ * `file_paths.xml`, so [FileProvider] can hand out a `content://` URI without further config.
+ * The receiver gets a read-permission grant via [Intent.FLAG_GRANT_READ_URI_PERMISSION] that
+ * lasts only for the duration of the share.
+ */
+fun shareIcs(
+    context: Context,
+    filename: String,
+    content: String,
+) {
+    val dir = File(context.cacheDir, "calendar").apply { mkdirs() }
+    val file = File(dir, filename)
+    file.writeText(content)
+
+    val uri = FileProvider.getUriForFile(context, "${context.packageName}.provider", file)
+    val intent =
+        Intent(Intent.ACTION_SEND).apply {
+            type = "text/calendar"
+            putExtra(Intent.EXTRA_STREAM, uri)
+            addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+            addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+        }
+    val chooser =
+        Intent
+            .createChooser(intent, stringRes(context, R.string.calendar_export_share_title))
+            .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+    context.startActivity(chooser)
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/NewCalendarButton.kt

@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import androidx.compose.animation.AnimatedVisibility
+import androidx.compose.animation.fadeIn
+import androidx.compose.animation.fadeOut
+import androidx.compose.animation.slideInVertically
+import androidx.compose.animation.slideOutVertically
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.material3.FloatingActionButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
+import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.amethyst.ui.theme.Size26Modifier
+import com.vitorpamplona.amethyst.ui.theme.Size55Modifier
+
+@Composable
+fun NewCalendarButton(nav: INav) {
+    var isOpen by remember { mutableStateOf(false) }
+
+    Column {
+        AnimatedVisibility(
+            visible = isOpen,
+            enter = slideInVertically(initialOffsetY = { it / 2 }) + fadeIn(),
+            exit = slideOutVertically(targetOffsetY = { it / 2 }) + fadeOut(),
+        ) {
+            Column {
+                FloatingActionButton(
+                    onClick = {
+                        isOpen = false
+                        nav.nav(Route.NewCalendarCollection())
+                    },
+                    modifier = Size55Modifier,
+                    shape = CircleShape,
+                    containerColor = MaterialTheme.colorScheme.primary,
+                ) {
+                    Icon(
+                        symbol = MaterialSymbols.CalendarMonth,
+                        // Spell out the full intent for screen readers — the bare "New collection"
+                        // string is ambiguous out of context.
+                        contentDescription = stringRes(R.string.calendar_fab_new_collection),
+                        modifier = Size26Modifier,
+                        tint = Color.White,
+                    )
+                }
+
+                Spacer(modifier = Modifier.height(20.dp))
+
+                FloatingActionButton(
+                    onClick = {
+                        isOpen = false
+                        nav.nav(Route.NewCalendarEvent())
+                    },
+                    modifier = Size55Modifier,
+                    shape = CircleShape,
+                    containerColor = MaterialTheme.colorScheme.primary,
+                ) {
+                    Icon(
+                        symbol = MaterialSymbols.Add,
+                        contentDescription = stringRes(R.string.calendar_fab_new_event),
+                        modifier = Size26Modifier,
+                        tint = Color.White,
+                    )
+                }
+
+                Spacer(modifier = Modifier.height(20.dp))
+            }
+        }
+
+        FloatingActionButton(
+            onClick = { isOpen = !isOpen },
+            modifier = Size55Modifier,
+            shape = CircleShape,
+            containerColor = MaterialTheme.colorScheme.primary,
+        ) {
+            AnimatedVisibility(
+                visible = isOpen,
+                enter = fadeIn(),
+                exit = fadeOut(),
+            ) {
+                Icon(
+                    symbol = MaterialSymbols.Close,
+                    contentDescription = stringRes(R.string.calendar_fab_toggle),
+                    modifier = Size26Modifier,
+                    tint = Color.White,
+                )
+            }
+
+            AnimatedVisibility(
+                visible = !isOpen,
+                enter = fadeIn(),
+                exit = fadeOut(),
+            ) {
+                Icon(
+                    symbol = MaterialSymbols.Add,
+                    // Top FAB toggles the sub-FABs in/out — describe that, not the sub-action.
+                    contentDescription = stringRes(R.string.calendar_fab_toggle),
+                    modifier = Size26Modifier,
+                    tint = Color.White,
+                )
+            }
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/create/CalendarDateTimePickerButton.kt

@@ -0,0 +1,193 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.create
+
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.material3.DatePicker
+import androidx.compose.material3.DatePickerDialog
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.material3.TimePicker
+import androidx.compose.material3.TimePickerDialog
+import androidx.compose.material3.rememberDatePickerState
+import androidx.compose.material3.rememberTimePickerState
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.ui.stringRes
+import java.text.DateFormat
+import java.text.SimpleDateFormat
+import java.time.Instant
+import java.time.ZoneId
+import java.time.ZoneOffset
+import java.util.Date
+import java.util.Locale
+
+/**
+ * Tap-to-edit button that opens a Material3 DatePicker (and, when [includeTime] is true,
+ * chains into a TimePicker). The resolved instant is converted to UTC epoch seconds using
+ * the device's zone offset *at the picked moment*, so DST transitions are handled correctly.
+ *
+ * Pass `0L` for [unixSeconds] when the user hasn't picked anything yet — the button shows
+ * [placeholder] instead.
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun CalendarDateTimePickerButton(
+    unixSeconds: Long,
+    placeholder: String,
+    includeTime: Boolean,
+    onChange: (Long) -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    var showDate by remember { mutableStateOf(false) }
+    var showTime by remember { mutableStateOf(false) }
+
+    val pretty =
+        if (unixSeconds <= 0L) {
+            placeholder
+        } else if (includeTime) {
+            DateFormat
+                .getDateTimeInstance(DateFormat.MEDIUM, DateFormat.SHORT)
+                .format(Date(unixSeconds * 1000))
+        } else {
+            SimpleDateFormat("EEEE, MMMM d, yyyy", Locale.getDefault()).format(Date(unixSeconds * 1000))
+        }
+
+    val initialMillis = if (unixSeconds > 0L) unixSeconds * 1000L else System.currentTimeMillis()
+    val initialLocal =
+        Instant
+            .ofEpochMilli(initialMillis)
+            .atZone(ZoneId.systemDefault())
+            .toLocalDateTime()
+
+    val datePickerState =
+        rememberDatePickerState(
+            initialSelectedDateMillis = initialMillis,
+        )
+    val timePickerState =
+        rememberTimePickerState(
+            initialHour = initialLocal.hour,
+            initialMinute = initialLocal.minute,
+            is24Hour = false,
+        )
+
+    fun reset() {
+        datePickerState.selectedDateMillis = initialMillis
+        timePickerState.hour = initialLocal.hour
+        timePickerState.minute = initialLocal.minute
+    }
+
+    OutlinedButton(
+        onClick = { showDate = true },
+        modifier = modifier.fillMaxWidth(),
+    ) {
+        Text(pretty)
+    }
+
+    if (showDate) {
+        DatePickerDialog(
+            onDismissRequest = {
+                reset()
+                showDate = false
+            },
+            confirmButton = {
+                TextButton(onClick = {
+                    showDate = false
+                    if (includeTime) {
+                        showTime = true
+                    } else {
+                        commit(datePickerState.selectedDateMillis, includeTime = false, hour = 0, minute = 0, onChange = onChange)
+                    }
+                }) { Text(stringRes(R.string.confirm)) }
+            },
+            dismissButton = {
+                TextButton(onClick = {
+                    reset()
+                    showDate = false
+                }) { Text(stringRes(R.string.cancel)) }
+            },
+        ) {
+            DatePicker(state = datePickerState)
+        }
+    }
+
+    if (showTime) {
+        TimePickerDialog(
+            title = { Text(stringRes(R.string.calendar_event_pick_time)) },
+            onDismissRequest = {
+                reset()
+                showTime = false
+            },
+            confirmButton = {
+                TextButton(onClick = {
+                    commit(
+                        dayMillisUtc = datePickerState.selectedDateMillis,
+                        includeTime = true,
+                        hour = timePickerState.hour,
+                        minute = timePickerState.minute,
+                        onChange = onChange,
+                    )
+                    showTime = false
+                }) { Text(stringRes(R.string.confirm)) }
+            },
+            dismissButton = {
+                TextButton(onClick = {
+                    reset()
+                    showTime = false
+                }) { Text(stringRes(R.string.cancel)) }
+            },
+        ) {
+            TimePicker(state = timePickerState)
+        }
+    }
+}
+
+private fun commit(
+    dayMillisUtc: Long?,
+    includeTime: Boolean,
+    hour: Int,
+    minute: Int,
+    onChange: (Long) -> Unit,
+) {
+    if (dayMillisUtc == null) return
+    val zone = ZoneId.systemDefault()
+    val localDate =
+        Instant
+            .ofEpochMilli(dayMillisUtc)
+            .atZone(ZoneOffset.UTC)
+            .toLocalDate()
+    val picked =
+        if (includeTime) {
+            localDate.atTime(hour, minute).atZone(zone).toEpochSecond()
+        } else {
+            // For date-only events, anchor to midnight in the user's local zone so the day
+            // boundary matches their wall-clock intent.
+            localDate.atStartOfDay(zone).toEpochSecond()
+        }
+    onChange(picked)
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/create/NewCalendarCollectionScreen.kt

@@ -0,0 +1,262 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.create
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.consumeWindowInsets
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.imePadding
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.ButtonDefaults
+import androidx.compose.material3.Checkbox
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.input.KeyboardCapitalization
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.viewmodel.compose.viewModel
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.topbars.SavingTopBar
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.formatLongDate
+import com.vitorpamplona.amethyst.ui.stringRes
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun NewCalendarCollectionScreen(
+    nav: INav,
+    accountViewModel: AccountViewModel,
+    editDTag: String? = null,
+) {
+    val vm: NewCalendarCollectionViewModel = viewModel()
+    vm.init(accountViewModel, editDTag)
+
+    Scaffold(
+        topBar = {
+            SavingTopBar(
+                titleRes = if (editDTag == null) R.string.new_calendar_collection else R.string.edit_calendar_collection,
+                onCancel = { nav.popBack() },
+                onPost = {
+                    accountViewModel.launchSigner {
+                        if (vm.publish()) {
+                            nav.popBack()
+                        }
+                    }
+                },
+            )
+        },
+    ) { pad ->
+        Column(
+            modifier =
+                Modifier
+                    .padding(
+                        start = 16.dp,
+                        end = 16.dp,
+                        top = pad.calculateTopPadding(),
+                        bottom = pad.calculateBottomPadding(),
+                    ).consumeWindowInsets(pad)
+                    .imePadding()
+                    .verticalScroll(rememberScrollState()),
+            verticalArrangement = Arrangement.spacedBy(12.dp),
+        ) {
+            OutlinedTextField(
+                value = vm.title.value,
+                onValueChange = { vm.title.value = it },
+                label = { Text(stringRes(R.string.calendar_collection_title)) },
+                modifier = Modifier.fillMaxWidth(),
+                singleLine = true,
+                keyboardOptions = KeyboardOptions(capitalization = KeyboardCapitalization.Sentences),
+                isError = !vm.isValid(),
+            )
+
+            OutlinedTextField(
+                value = vm.description.value,
+                onValueChange = { vm.description.value = it },
+                label = { Text(stringRes(R.string.calendar_collection_description)) },
+                modifier = Modifier.fillMaxWidth(),
+                minLines = 4,
+                keyboardOptions = KeyboardOptions(capitalization = KeyboardCapitalization.Sentences),
+            )
+
+            if (!vm.isValid()) {
+                Text(
+                    text = stringRes(R.string.calendar_collection_invalid),
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.error,
+                )
+            }
+
+            AppointmentPickerSection(vm)
+
+            if (vm.isEditing) {
+                DeleteCalendarRow(vm = vm, onDeleted = { nav.popBack() }, accountViewModel = accountViewModel)
+            }
+        }
+    }
+}
+
+@Composable
+private fun DeleteCalendarRow(
+    vm: NewCalendarCollectionViewModel,
+    onDeleted: () -> Unit,
+    accountViewModel: AccountViewModel,
+) {
+    var confirming by rememberSaveable { mutableStateOf(false) }
+
+    OutlinedButton(
+        onClick = { confirming = true },
+        modifier = Modifier.fillMaxWidth(),
+        colors = ButtonDefaults.outlinedButtonColors(contentColor = MaterialTheme.colorScheme.error),
+    ) {
+        Text(text = stringRes(R.string.calendar_collection_delete))
+    }
+
+    if (confirming) {
+        AlertDialog(
+            onDismissRequest = { confirming = false },
+            title = { Text(stringRes(R.string.calendar_collection_delete_confirm_title)) },
+            text = { Text(stringRes(R.string.calendar_collection_delete_confirm_message)) },
+            confirmButton = {
+                TextButton(onClick = {
+                    confirming = false
+                    accountViewModel.launchSigner {
+                        if (vm.deleteLoaded()) onDeleted()
+                    }
+                }) {
+                    Text(
+                        text = stringRes(R.string.calendar_collection_delete),
+                        color = MaterialTheme.colorScheme.error,
+                    )
+                }
+            },
+            dismissButton = {
+                TextButton(onClick = { confirming = false }) {
+                    Text(stringRes(R.string.cancel))
+                }
+            },
+        )
+    }
+}
+
+@Composable
+private fun AppointmentPickerSection(vm: NewCalendarCollectionViewModel) {
+    val available by vm.availableAppointments
+    val selectedCount = vm.selectedAddresses.size
+
+    Text(
+        text = stringRes(R.string.calendar_collection_events_section, selectedCount),
+        style = MaterialTheme.typography.titleSmall,
+        fontWeight = FontWeight.Bold,
+        color = MaterialTheme.colorScheme.primary,
+        modifier = Modifier.padding(top = 8.dp),
+    )
+
+    if (available.isEmpty()) {
+        Text(
+            text = stringRes(R.string.calendar_collection_no_events_yet),
+            style = MaterialTheme.typography.bodySmall,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+            modifier = Modifier.padding(vertical = 8.dp),
+        )
+        return
+    }
+
+    available.forEach { summary ->
+        // Snapshot selection state without subscribing to the list itself (we only need to
+        // re-render the affected row on toggle).
+        val isSelected = vm.selectedAddresses.contains(summary.address)
+        AppointmentPickerRow(
+            summary = summary,
+            isSelected = isSelected,
+            onToggle = { vm.toggle(summary.address) },
+        )
+        HorizontalDivider()
+    }
+}
+
+@Composable
+private fun AppointmentPickerRow(
+    summary: OwnedAppointmentSummary,
+    isSelected: Boolean,
+    onToggle: () -> Unit,
+) {
+    // `stringRes` must be called outside `remember` (it's @Composable). The date format is the
+    // only piece worth memoising — the localised "All-day" label is a single lookup per row.
+    val allDayLabel = stringRes(R.string.calendar_all_day)
+    val whenLabel =
+        remember(summary.address, summary.startSeconds, summary.isAllDay, allDayLabel) {
+            when {
+                summary.isAllDay -> allDayLabel
+                summary.startSeconds != null -> formatLongDate(summary.startSeconds)
+                else -> "—"
+            }
+        }
+
+    Row(
+        modifier =
+            Modifier
+                .fillMaxWidth()
+                .clickable(onClick = onToggle)
+                .padding(vertical = 8.dp),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Checkbox(checked = isSelected, onCheckedChange = { onToggle() })
+        Column(
+            modifier = Modifier.padding(start = 4.dp),
+            verticalArrangement = Arrangement.spacedBy(2.dp),
+        ) {
+            Text(
+                text = summary.title.ifBlank { stringRes(R.string.calendar_untitled) },
+                style = MaterialTheme.typography.bodyLarge,
+                maxLines = 1,
+                overflow = TextOverflow.Ellipsis,
+            )
+            Text(
+                text = whenLabel,
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/create/NewCalendarCollectionViewModel.kt

@@ -0,0 +1,208 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.create
+
+import androidx.compose.runtime.Immutable
+import androidx.compose.runtime.mutableStateListOf
+import androidx.compose.runtime.mutableStateOf
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.vitorpamplona.amethyst.model.Account
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip01Core.tags.aTag.ATag
+import com.vitorpamplona.quartz.nip01Core.tags.aTag.aTags
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+import com.vitorpamplona.quartz.utils.TimeUtils
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.launch
+
+/**
+ * Lightweight projection of a calendar appointment authored by the current user, used to power
+ * the multi-select picker on the collection editor.
+ */
+@Immutable
+data class OwnedAppointmentSummary(
+    val address: Address,
+    val title: String,
+    val startSeconds: Long?,
+    val isAllDay: Boolean,
+)
+
+class NewCalendarCollectionViewModel : ViewModel() {
+    private lateinit var account: Account
+
+    val title = mutableStateOf("")
+    val description = mutableStateOf("")
+    val isPublishing = mutableStateOf(false)
+
+    /** Stable d-tag for the addressable: random for create, preserved when editing. */
+    private var dTag: String? = null
+
+    /** The full original event in edit mode; needed to publish a NIP-09 deletion. */
+    private var loadedEvent: com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent? = null
+
+    val selectedAddresses = mutableStateListOf<Address>()
+    val availableAppointments = mutableStateOf<List<OwnedAppointmentSummary>>(emptyList())
+
+    private var liveScanJob: Job? = null
+
+    val isEditing: Boolean
+        get() = dTag != null
+
+    fun init(
+        accountViewModel: AccountViewModel,
+        editDTag: String?,
+    ) {
+        if (::account.isInitialized) return // idempotent across recompositions
+        this.account = accountViewModel.account
+        dTag = editDTag
+
+        editDTag?.let { existingDTag ->
+            val existingAddress = Address(CalendarEvent.KIND, account.userProfile().pubkeyHex, existingDTag)
+            val existingNote = LocalCache.addressables.get(existingAddress)
+            (existingNote?.event as? CalendarEvent)?.let { existing ->
+                loadedEvent = existing
+                title.value = existing.title().orEmpty()
+                description.value = existing.content
+                selectedAddresses.addAll(existing.calendarEventAddresses())
+            }
+        }
+
+        availableAppointments.value = loadOwnedAppointments()
+
+        // Reactively re-scan when new events arrive in LocalCache. Without this, an appointment
+        // the user publishes from another screen (or that arrives from a relay) while the editor
+        // is open wouldn't appear in the picker until the screen reopens. The Job is stored so
+        // re-init in editing-mode doesn't stack subscribers (init() returns early after the
+        // first call anyway, but defence in depth).
+        liveScanJob?.cancel()
+        liveScanJob =
+            viewModelScope.launch(Dispatchers.IO) {
+                LocalCache.live.newEventBundles.collect {
+                    availableAppointments.value = loadOwnedAppointments()
+                }
+            }
+    }
+
+    override fun onCleared() {
+        liveScanJob?.cancel()
+        super.onCleared()
+    }
+
+    fun toggle(address: Address) {
+        if (selectedAddresses.remove(address)) return
+        selectedAddresses.add(address)
+    }
+
+    /**
+     * Publishes a NIP-09 deletion event for the loaded calendar. No-op when called outside
+     * edit mode (we wouldn't have a target to delete). Returns true when the deletion was
+     * dispatched so the caller can pop back.
+     */
+    suspend fun deleteLoaded(): Boolean {
+        val target = loadedEvent ?: return false
+        account.delete(target, emptySet())
+        return true
+    }
+
+    fun isValid(): Boolean = title.value.isNotBlank()
+
+    suspend fun publish(): Boolean {
+        if (!isValid()) return false
+        isPublishing.value = true
+        try {
+            val effectiveDTag = dTag
+            val selected = selectedAddresses.toList()
+            val parsedTitle = title.value.trim()
+            val parsedDescription = description.value.trim()
+
+            account.signAndComputeBroadcast(
+                if (effectiveDTag != null) {
+                    CalendarEvent.build(
+                        title = parsedTitle,
+                        content = parsedDescription,
+                        dTag = effectiveDTag,
+                    ) {
+                        if (selected.isNotEmpty()) aTags(selected.map { ATag(it) })
+                    }
+                } else {
+                    CalendarEvent.build(
+                        title = parsedTitle,
+                        content = parsedDescription,
+                    ) {
+                        if (selected.isNotEmpty()) aTags(selected.map { ATag(it) })
+                    }
+                },
+            )
+            return true
+        } finally {
+            isPublishing.value = false
+        }
+    }
+
+    private fun loadOwnedAppointments(): List<OwnedAppointmentSummary> {
+        val mePubKey = account.userProfile().pubkeyHex
+        val results =
+            LocalCache.notes
+                .filterIntoSet { _, note ->
+                    val e = note.event
+                    (e is CalendarTimeSlotEvent || e is CalendarDateSlotEvent) && e.pubKey == mePubKey
+                }.mapNotNull { note ->
+                    when (val e = note.event) {
+                        is CalendarTimeSlotEvent ->
+                            OwnedAppointmentSummary(
+                                address = e.address(),
+                                // `title` may be empty; the picker row substitutes a localised
+                                // "(untitled)" string at render time — the VM stays string-free.
+                                title = e.title().orEmpty(),
+                                startSeconds = e.start(),
+                                isAllDay = false,
+                            )
+                        is CalendarDateSlotEvent ->
+                            OwnedAppointmentSummary(
+                                address = e.address(),
+                                // `title` may be empty; the picker row substitutes a localised
+                                // "(untitled)" string at render time — the VM stays string-free.
+                                title = e.title().orEmpty(),
+                                // Date-only events don't have an instant; null sorts last in the
+                                // upcoming-first comparator below.
+                                startSeconds = null,
+                                isAllDay = true,
+                            )
+                        else -> null
+                    }
+                }
+        // Upcoming events first (closest start), then date-only/past — same intent as the
+        // main feed's UpcomingFirst ordering, simplified for the picker context.
+        val now = TimeUtils.now()
+        return results.sortedWith(
+            compareBy(
+                { if (it.startSeconds == null || it.startSeconds >= now) 0 else 1 },
+                { it.startSeconds ?: Long.MAX_VALUE },
+            ),
+        )
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/create/NewCalendarEventScreen.kt

@@ -0,0 +1,382 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.create
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.consumeWindowInsets
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.imePadding
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Switch
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.input.KeyboardCapitalization
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.viewmodel.compose.viewModel
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
+import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.topbars.SavingTopBar
+import com.vitorpamplona.amethyst.ui.note.ClickableUserPicture
+import com.vitorpamplona.amethyst.ui.note.UsernameDisplay
+import com.vitorpamplona.amethyst.ui.note.creators.userSuggestions.ShowUserSuggestionList
+import com.vitorpamplona.amethyst.ui.note.creators.userSuggestions.UserSuggestionState
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.rooms.LoadUser
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.amethyst.ui.theme.Size30dp
+import com.vitorpamplona.amethyst.ui.theme.SuggestionListDefaultHeightChat
+import kotlinx.coroutines.launch
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun NewCalendarEventScreen(
+    nav: INav,
+    accountViewModel: AccountViewModel,
+    editKind: Int? = null,
+    editPubKeyHex: String? = null,
+    editDTag: String? = null,
+) {
+    val vm: NewCalendarEventViewModel = viewModel()
+    vm.init(accountViewModel)
+    if (editKind != null && editPubKeyHex != null && editDTag != null) {
+        // loadForEdit is idempotent across recompositions; safe to call from the composable body.
+        vm.loadForEdit(accountViewModel, editKind, editPubKeyHex, editDTag)
+    }
+
+    Scaffold(
+        topBar = {
+            SavingTopBar(
+                titleRes = if (vm.isEditing) R.string.edit_calendar_event else R.string.new_calendar_event,
+                onCancel = { nav.popBack() },
+                onPost = {
+                    accountViewModel.launchSigner {
+                        if (vm.publish()) {
+                            nav.popBack()
+                        }
+                    }
+                },
+            )
+        },
+    ) { pad ->
+        Column(
+            modifier =
+                Modifier
+                    .padding(
+                        start = 16.dp,
+                        end = 16.dp,
+                        top = pad.calculateTopPadding(),
+                        bottom = pad.calculateBottomPadding(),
+                    ).consumeWindowInsets(pad)
+                    .imePadding()
+                    .verticalScroll(rememberScrollState()),
+            verticalArrangement = Arrangement.spacedBy(12.dp),
+        ) {
+            AllDayToggleRow(vm)
+
+            OutlinedTextField(
+                value = vm.title.value,
+                onValueChange = { vm.title.value = it },
+                label = { Text(stringRes(R.string.calendar_event_title)) },
+                modifier = Modifier.fillMaxWidth(),
+                singleLine = true,
+                keyboardOptions = KeyboardOptions(capitalization = KeyboardCapitalization.Sentences),
+            )
+
+            val isAllDay by vm.isAllDay
+            FieldLabel(stringRes(R.string.calendar_event_start))
+            CalendarDateTimePickerButton(
+                unixSeconds = vm.startSeconds.value,
+                placeholder = stringRes(R.string.calendar_event_pick_date),
+                includeTime = !isAllDay,
+                onChange = { vm.startSeconds.value = it },
+            )
+
+            FieldLabel(stringRes(R.string.calendar_event_end))
+            CalendarDateTimePickerButton(
+                unixSeconds = vm.endSeconds.value,
+                placeholder = stringRes(R.string.calendar_event_pick_date),
+                includeTime = !isAllDay,
+                onChange = { vm.endSeconds.value = it },
+            )
+
+            OutlinedTextField(
+                value = vm.location.value,
+                onValueChange = { vm.location.value = it },
+                label = { Text(stringRes(R.string.calendar_event_location)) },
+                modifier = Modifier.fillMaxWidth(),
+                singleLine = true,
+            )
+
+            OutlinedTextField(
+                value = vm.summary.value,
+                onValueChange = { vm.summary.value = it },
+                label = { Text(stringRes(R.string.calendar_event_summary)) },
+                modifier = Modifier.fillMaxWidth(),
+                minLines = 3,
+                keyboardOptions = KeyboardOptions(capitalization = KeyboardCapitalization.Sentences),
+            )
+
+            ImageRow(vm = vm, accountViewModel = accountViewModel)
+
+            OutlinedTextField(
+                value = vm.hashtags.value,
+                onValueChange = { vm.hashtags.value = it },
+                label = { Text(stringRes(R.string.calendar_event_hashtags)) },
+                modifier = Modifier.fillMaxWidth(),
+                singleLine = true,
+            )
+
+            ParticipantsRow(vm = vm, accountViewModel = accountViewModel)
+
+            if (!vm.isValid()) {
+                Text(
+                    text = stringRes(R.string.calendar_event_invalid),
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.error,
+                )
+            } else if (!vm.isEndAfterStart()) {
+                Text(
+                    text = stringRes(R.string.calendar_event_end_before_start),
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.error,
+                )
+            }
+
+            Spacer(modifier = Modifier.height(24.dp))
+        }
+    }
+}
+
+@Composable
+private fun AllDayToggleRow(vm: NewCalendarEventViewModel) {
+    Row(
+        modifier = Modifier.fillMaxWidth(),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Column(modifier = Modifier.weight(1f)) {
+            Text(
+                text = stringRes(R.string.calendar_event_all_day),
+                style = MaterialTheme.typography.titleSmall,
+            )
+            if (vm.isEditing) {
+                // Toggling all-day mid-edit would mean a different event kind (31922 vs 31923)
+                // and a different addressable, leaving the original event live as a stale copy.
+                // The user can delete the appointment and re-create if they want to change kind.
+                Text(
+                    text = stringRes(R.string.calendar_event_all_day_locked),
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                )
+            }
+        }
+        Switch(
+            checked = vm.isAllDay.value,
+            onCheckedChange = { vm.isAllDay.value = it },
+            enabled = !vm.isEditing,
+        )
+    }
+}
+
+@Composable
+private fun FieldLabel(text: String) {
+    Text(
+        text = text,
+        style = MaterialTheme.typography.labelMedium,
+        color = MaterialTheme.colorScheme.onSurfaceVariant,
+        fontWeight = FontWeight.SemiBold,
+        modifier = Modifier.padding(start = 4.dp),
+    )
+}
+
+/**
+ * URL field + gallery-picker icon. Tapping the icon launches the system picker; once the user
+ * picks an image we hand it to [NewCalendarEventViewModel.uploadAndSetImage], which sends it
+ * to the user's configured file server (Blossom / NIP-96 / NIP-95) and writes the resulting
+ * URL into [vm.imageUrl]. A small inline progress indicator covers the upload window.
+ */
+@Composable
+private fun ImageRow(
+    vm: NewCalendarEventViewModel,
+    accountViewModel: AccountViewModel,
+) {
+    val context = LocalContext.current
+    val scope = rememberCoroutineScope()
+    val launcher =
+        androidx.activity.compose.rememberLauncherForActivityResult(
+            contract =
+                androidx.activity.result.contract.ActivityResultContracts
+                    .GetContent(),
+        ) { uri ->
+            if (uri == null) return@rememberLauncherForActivityResult
+            val mime = context.contentResolver.getType(uri)
+            scope.launch {
+                val ok = vm.uploadAndSetImage(uri, mime, context)
+                if (!ok) {
+                    accountViewModel.toastManager.toast(
+                        R.string.calendar_event_image_upload_failed,
+                        R.string.calendar_event_image_upload_failed_body,
+                    )
+                }
+            }
+        }
+
+    Row(modifier = Modifier.fillMaxWidth(), verticalAlignment = Alignment.CenterVertically) {
+        OutlinedTextField(
+            value = vm.imageUrl.value,
+            onValueChange = { vm.imageUrl.value = it },
+            label = { Text(stringRes(R.string.calendar_event_image)) },
+            modifier = Modifier.weight(1f),
+            singleLine = true,
+            enabled = !vm.isUploadingImage.value,
+        )
+        if (vm.isUploadingImage.value) {
+            CircularProgressIndicator(
+                modifier = Modifier.padding(start = 8.dp).size(20.dp),
+                strokeWidth = 2.dp,
+            )
+        } else {
+            IconButton(onClick = { launcher.launch("image/*") }) {
+                Icon(
+                    symbol = MaterialSymbols.AddPhotoAlternate,
+                    contentDescription = stringRes(R.string.calendar_event_pick_image),
+                    modifier = Modifier.size(22.dp),
+                    tint = MaterialTheme.colorScheme.primary,
+                )
+            }
+        }
+    }
+}
+
+/**
+ * Inline participant picker. The simplest workable shape: a single-line OutlinedTextField that
+ * accepts a 64-hex pubkey or an npub, and an "Add" button that pushes it into the list. The
+ * current participants render as a column of [UserRow] entries with an X button each.
+ *
+ * Search-by-display-name is an obvious follow-up but the field accepting npubs directly is the
+ * primary nostr-native flow today; copy-pasting an npub from a profile is how most users add
+ * collaborators in other apps.
+ */
+@Composable
+private fun ParticipantsRow(
+    vm: NewCalendarEventViewModel,
+    accountViewModel: AccountViewModel,
+) {
+    // Same suggestion machinery the badge-award / DM / new-post screens use: type a name, npub,
+    // hex, or nip-05; the LazyColumn below shows live matches from the local cache + relay
+    // search; tapping a row adds the user to the participants list.
+    val userSuggestions =
+        remember { UserSuggestionState(accountViewModel.account, accountViewModel.nip05ClientBuilder()) }
+    DisposableEffect(Unit) { onDispose { userSuggestions.reset() } }
+
+    var searchInput by rememberSaveable { mutableStateOf("") }
+
+    Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        FieldLabel(stringRes(R.string.calendar_event_participants_section, vm.participants.size))
+
+        OutlinedTextField(
+            value = searchInput,
+            onValueChange = {
+                searchInput = it
+                if (it.length > 2) {
+                    userSuggestions.processCurrentWord(it)
+                } else {
+                    userSuggestions.reset()
+                }
+            },
+            label = { Text(stringRes(R.string.calendar_event_participant_input)) },
+            modifier = Modifier.fillMaxWidth(),
+            singleLine = true,
+        )
+
+        if (searchInput.length > 2) {
+            ShowUserSuggestionList(
+                userSuggestions = userSuggestions,
+                onSelect = { user ->
+                    vm.addParticipant(user.pubkeyHex)
+                    searchInput = ""
+                    userSuggestions.reset()
+                },
+                accountViewModel = accountViewModel,
+                modifier = SuggestionListDefaultHeightChat,
+            )
+        }
+
+        vm.participants.forEach { pubKey ->
+            Row(verticalAlignment = Alignment.CenterVertically) {
+                ClickableUserPicture(
+                    baseUserHex = pubKey,
+                    size = Size30dp,
+                    accountViewModel = accountViewModel,
+                )
+                LoadUser(baseUserHex = pubKey, accountViewModel = accountViewModel) { user ->
+                    if (user != null) {
+                        UsernameDisplay(
+                            baseUser = user,
+                            weight = Modifier.weight(1f).padding(horizontal = 8.dp),
+                            accountViewModel = accountViewModel,
+                        )
+                    } else {
+                        Text(
+                            text = pubKey.take(8) + "…" + pubKey.takeLast(8),
+                            style = MaterialTheme.typography.bodyMedium,
+                            modifier = Modifier.weight(1f).padding(horizontal = 8.dp),
+                        )
+                    }
+                }
+                IconButton(onClick = { vm.removeParticipant(pubKey) }) {
+                    Icon(
+                        symbol = MaterialSymbols.Close,
+                        contentDescription = stringRes(R.string.calendar_event_participant_remove),
+                        modifier = Modifier.size(18.dp),
+                        tint = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                }
+            }
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/create/NewCalendarEventViewModel.kt

@@ -0,0 +1,281 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.create
+
+import android.content.Context
+import android.net.Uri
+import androidx.compose.runtime.mutableStateOf
+import androidx.lifecycle.ViewModel
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.parseIsoDateToUnixSeconds
+import com.vitorpamplona.amethyst.model.Account
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.service.uploads.CompressorQuality
+import com.vitorpamplona.amethyst.service.uploads.UploadOrchestrator
+import com.vitorpamplona.amethyst.service.uploads.UploadingState
+import com.vitorpamplona.amethyst.ui.actions.mediaServers.DEFAULT_MEDIA_SERVERS
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip01Core.tags.hashtags.hashtags
+import com.vitorpamplona.quartz.nip01Core.tags.people.PTag
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import java.text.SimpleDateFormat
+import java.time.ZoneId
+import java.util.Locale
+import java.util.TimeZone
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.image as dayImage
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.locations as dayLocations
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.participants as dayParticipants
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.summary as daySummary
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.image as timeImage
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.locations as timeLocations
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.participants as timeParticipants
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.summary as timeSummary
+
+class NewCalendarEventViewModel : ViewModel() {
+    private lateinit var account: Account
+
+    val isAllDay = mutableStateOf(false)
+    val title = mutableStateOf("")
+    val summary = mutableStateOf("")
+    val location = mutableStateOf("")
+    val imageUrl = mutableStateOf("")
+    val hashtags = mutableStateOf("") // comma-separated
+
+    /** Start instant in epoch seconds. 0 means unset; the create screen guards against publishing without a real value. */
+    val startSeconds = mutableStateOf(0L)
+    val endSeconds = mutableStateOf(0L)
+
+    val isPublishing = mutableStateOf(false)
+    val isUploadingImage = mutableStateOf(false)
+
+    /** Participant pubkeys to embed as `p` tags on the published event. */
+    val participants = androidx.compose.runtime.mutableStateListOf<String>()
+
+    /**
+     * When non-null, [publish] preserves this d-tag and kind so the broadcast replaces an
+     * existing addressable appointment instead of minting a new one. The UI also locks the
+     * all-day toggle in edit mode — switching kinds mid-edit would leave a stale event under
+     * the original kind/d-tag combination.
+     */
+    private var editAddress: Address? = null
+
+    val isEditing: Boolean
+        get() = editAddress != null
+
+    fun init(accountViewModel: AccountViewModel) {
+        if (::account.isInitialized) return
+        this.account = accountViewModel.account
+    }
+
+    /**
+     * Pre-populate from an existing appointment for edit mode. Idempotent: a recomposition that
+     * calls this again is a no-op. Only the author of the appointment should reach this path —
+     * the screen guards via UI affordance, but [publish] will also produce an unsigned event if
+     * the current account doesn't own the address.
+     */
+    fun loadForEdit(
+        accountViewModel: AccountViewModel,
+        kind: Int,
+        pubKeyHex: String,
+        dTag: String,
+    ) {
+        init(accountViewModel)
+        if (editAddress != null) return // already loaded
+
+        val address = Address(kind, pubKeyHex, dTag)
+        val existing = LocalCache.addressables.get(address)?.event ?: return
+        editAddress = address
+
+        when (existing) {
+            is CalendarTimeSlotEvent -> {
+                isAllDay.value = false
+                title.value = existing.title().orEmpty()
+                summary.value = existing.summary().orEmpty().ifBlank { existing.content }
+                location.value = existing.location().orEmpty()
+                imageUrl.value = existing.image().orEmpty()
+                hashtags.value = existing.hashtags().joinToString(", ")
+                startSeconds.value = existing.start() ?: 0L
+                endSeconds.value = existing.end() ?: 0L
+                participants.clear()
+                participants.addAll(existing.participants().map { it.pubKey })
+            }
+            is CalendarDateSlotEvent -> {
+                isAllDay.value = true
+                title.value = existing.title().orEmpty()
+                summary.value = existing.summary().orEmpty().ifBlank { existing.content }
+                location.value = existing.location().orEmpty()
+                imageUrl.value = existing.image().orEmpty()
+                hashtags.value = existing.hashtags().joinToString(", ")
+                startSeconds.value = parseIsoDateToUnixSeconds(existing.start()) ?: 0L
+                endSeconds.value = parseIsoDateToUnixSeconds(existing.end()) ?: 0L
+                participants.clear()
+                participants.addAll(existing.participants().map { it.pubKey })
+            }
+        }
+    }
+
+    fun isValid(): Boolean = title.value.isNotBlank() && startSeconds.value > 0L
+
+    fun isEndAfterStart(): Boolean = endSeconds.value == 0L || endSeconds.value >= startSeconds.value
+
+    fun addParticipant(pubKeyHex: String) {
+        val trimmed = pubKeyHex.trim()
+        if (trimmed.isBlank() || trimmed in participants) return
+        participants.add(trimmed)
+    }
+
+    fun removeParticipant(pubKeyHex: String) {
+        participants.remove(pubKeyHex)
+    }
+
+    /**
+     * Picks a single image from the gallery → uploads to the user's default file server →
+     * writes the resulting URL into [imageUrl]. Returns true on success so the screen can
+     * surface a toast on failure. Wraps [UploadOrchestrator.upload] with sensible defaults
+     * (MEDIUM quality, strip metadata, no content warning) so the calendar create screen
+     * doesn't have to drag in NewMediaModel's full surface area.
+     */
+    suspend fun uploadAndSetImage(
+        uri: Uri,
+        mimeType: String?,
+        context: Context,
+    ): Boolean {
+        if (!::account.isInitialized) return false
+        isUploadingImage.value = true
+        try {
+            val server = account.settings.defaultFileServer ?: DEFAULT_MEDIA_SERVERS[0]
+            val result =
+                UploadOrchestrator().upload(
+                    uri = uri,
+                    mimeType = mimeType,
+                    alt = title.value.ifBlank { null },
+                    contentWarningReason = null,
+                    compressionQuality = CompressorQuality.MEDIUM,
+                    server = server,
+                    account = account,
+                    context = context,
+                )
+            val serverResult =
+                (result as? UploadingState.Finished)?.result as? UploadOrchestrator.OrchestratorResult.ServerResult
+            return serverResult?.url?.also { imageUrl.value = it } != null
+        } finally {
+            isUploadingImage.value = false
+        }
+    }
+
+    suspend fun publish(): Boolean {
+        if (!isValid() || !isEndAfterStart()) return false
+        isPublishing.value = true
+        try {
+            val parsedHashtags =
+                hashtags.value
+                    .split(',', '\n', ' ')
+                    .map { it.trim().trimStart('#') }
+                    .filter { it.isNotBlank() }
+            val parsedSummary = summary.value.trim().takeIf { it.isNotBlank() }
+            val parsedImage = imageUrl.value.trim().takeIf { it.isNotBlank() }
+            val parsedLocation = location.value.trim().takeIf { it.isNotBlank() }
+            val parsedParticipants = participants.map { PTag(it) }
+            val tzId = TimeZone.getDefault().id
+            val targetDTag = editAddress?.dTag
+
+            if (isAllDay.value) {
+                account.signAndComputeBroadcast(
+                    if (targetDTag != null) {
+                        CalendarDateSlotEvent.build(
+                            title = title.value.trim(),
+                            start = toIsoDate(startSeconds.value),
+                            end = endSeconds.value.takeIf { it > 0L }?.let { toIsoDate(it) },
+                            content = parsedSummary.orEmpty(),
+                            dTag = targetDTag,
+                        ) {
+                            parsedSummary?.let { daySummary(it) }
+                            parsedImage?.let { dayImage(it) }
+                            parsedLocation?.let { dayLocations(listOf(it)) }
+                            if (parsedHashtags.isNotEmpty()) hashtags(parsedHashtags)
+                            if (parsedParticipants.isNotEmpty()) dayParticipants(parsedParticipants)
+                        }
+                    } else {
+                        CalendarDateSlotEvent.build(
+                            title = title.value.trim(),
+                            start = toIsoDate(startSeconds.value),
+                            end = endSeconds.value.takeIf { it > 0L }?.let { toIsoDate(it) },
+                            content = parsedSummary.orEmpty(),
+                        ) {
+                            parsedSummary?.let { daySummary(it) }
+                            parsedImage?.let { dayImage(it) }
+                            parsedLocation?.let { dayLocations(listOf(it)) }
+                            if (parsedHashtags.isNotEmpty()) hashtags(parsedHashtags)
+                            if (parsedParticipants.isNotEmpty()) dayParticipants(parsedParticipants)
+                        }
+                    },
+                )
+            } else {
+                account.signAndComputeBroadcast(
+                    if (targetDTag != null) {
+                        CalendarTimeSlotEvent.build(
+                            title = title.value.trim(),
+                            start = startSeconds.value,
+                            end = endSeconds.value.takeIf { it > 0L },
+                            startTzId = tzId,
+                            endTzId = tzId,
+                            content = parsedSummary.orEmpty(),
+                            dTag = targetDTag,
+                        ) {
+                            parsedSummary?.let { timeSummary(it) }
+                            parsedImage?.let { timeImage(it) }
+                            parsedLocation?.let { timeLocations(listOf(it)) }
+                            if (parsedHashtags.isNotEmpty()) hashtags(parsedHashtags)
+                            if (parsedParticipants.isNotEmpty()) timeParticipants(parsedParticipants)
+                        }
+                    } else {
+                        CalendarTimeSlotEvent.build(
+                            title = title.value.trim(),
+                            start = startSeconds.value,
+                            end = endSeconds.value.takeIf { it > 0L },
+                            startTzId = tzId,
+                            endTzId = tzId,
+                            content = parsedSummary.orEmpty(),
+                        ) {
+                            parsedSummary?.let { timeSummary(it) }
+                            parsedImage?.let { timeImage(it) }
+                            parsedLocation?.let { timeLocations(listOf(it)) }
+                            if (parsedHashtags.isNotEmpty()) hashtags(parsedHashtags)
+                            if (parsedParticipants.isNotEmpty()) timeParticipants(parsedParticipants)
+                        }
+                    },
+                )
+            }
+            return true
+        } finally {
+            isPublishing.value = false
+        }
+    }
+}
+
+private val IsoFormat =
+    SimpleDateFormat("yyyy-MM-dd", Locale.US).apply {
+        // 31922 uses calendar-date strings; format the user's local date.
+        timeZone = TimeZone.getTimeZone(ZoneId.systemDefault())
+    }
+
+private fun toIsoDate(epochSeconds: Long): String = IsoFormat.format(java.util.Date(epochSeconds * 1000))

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/dal/CalendarAppointmentsFeedFilter.kt

@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal
+
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.upcomingFirstCalendarOrder
+import com.vitorpamplona.amethyst.model.Account
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.model.TopFilter
+import com.vitorpamplona.amethyst.ui.dal.AdditiveFeedFilter
+import com.vitorpamplona.amethyst.ui.dal.FilterByListParams
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+
+/**
+ * Feed of NIP-52 calendar *appointments* — kinds 31922 (date-slot) and 31923 (time-slot). The
+ * NIP calls kind 31924 a "calendar" (a list of appointments), so this filter intentionally does
+ * not load 31924; see [CalendarCollectionsFeedFilter] for that.
+ */
+class CalendarAppointmentsFeedFilter(
+    val account: Account,
+) : AdditiveFeedFilter<Note>() {
+    override fun feedKey(): String = account.userProfile().pubkeyHex + "-" + followList().code
+
+    override fun limit() = 500
+
+    fun followList(): TopFilter = account.settings.defaultCalendarsFollowList.value
+
+    private fun TopFilter.isMuteList() = this is TopFilter.MuteList
+
+    private fun TopFilter.isBlockList() = this is TopFilter.PeopleList && this.address == account.blockPeopleList.getBlockListAddress()
+
+    private fun TopFilter.wantsToSeeNegativeStuff() = isMuteList() || isBlockList()
+
+    override fun showHiddenKey(): Boolean = followList().wantsToSeeNegativeStuff()
+
+    override fun feed(): List<Note> {
+        val params = buildFilterParams(account)
+        val notes =
+            LocalCache.notes.filterIntoSet { _, it ->
+                val e = it.event
+                (e is CalendarTimeSlotEvent || e is CalendarDateSlotEvent) && params.match(e, it.relays)
+            }
+        return sort(notes)
+    }
+
+    override fun applyFilter(newItems: Set<Note>): Set<Note> = innerApplyFilter(newItems)
+
+    private fun buildFilterParams(account: Account): FilterByListParams =
+        FilterByListParams.create(
+            account.liveCalendarsFollowLists.value,
+            account.hiddenUsers.flow.value,
+        )
+
+    private fun innerApplyFilter(collection: Collection<Note>): Set<Note> {
+        val params = buildFilterParams(account)
+        return collection.filterTo(HashSet()) {
+            val e = it.event
+            (e is CalendarTimeSlotEvent || e is CalendarDateSlotEvent) && params.match(e, it.relays)
+        }
+    }
+
+    override fun sort(items: Set<Note>): List<Note> =
+        items.sortedWith(
+            upcomingFirstCalendarOrder(
+                com.vitorpamplona.quartz.utils.TimeUtils
+                    .now(),
+            ),
+        )
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/dal/CalendarCollectionsFeedFilter.kt

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal
+
+import com.vitorpamplona.amethyst.model.Account
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.model.TopFilter
+import com.vitorpamplona.amethyst.ui.dal.AdditiveFeedFilter
+import com.vitorpamplona.amethyst.ui.dal.DefaultFeedOrder
+import com.vitorpamplona.amethyst.ui.dal.FilterByListParams
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+
+class CalendarCollectionsFeedFilter(
+    val account: Account,
+) : AdditiveFeedFilter<Note>() {
+    override fun feedKey(): String = account.userProfile().pubkeyHex + "-collections-" + followList().code
+
+    override fun limit() = 200
+
+    fun followList(): TopFilter = account.settings.defaultCalendarsFollowList.value
+
+    private fun TopFilter.isMuteList() = this is TopFilter.MuteList
+
+    private fun TopFilter.isBlockList() = this is TopFilter.PeopleList && this.address == account.blockPeopleList.getBlockListAddress()
+
+    override fun showHiddenKey(): Boolean = followList().let { it.isMuteList() || it.isBlockList() }
+
+    override fun feed(): List<Note> {
+        val params = buildFilterParams(account)
+        val notes =
+            LocalCache.addressables.filterIntoSet { _, it ->
+                val e = it.event
+                e is CalendarEvent && params.match(e, it.relays)
+            }
+        return sort(notes)
+    }
+
+    override fun applyFilter(newItems: Set<Note>): Set<Note> = innerApplyFilter(newItems)
+
+    private fun buildFilterParams(account: Account): FilterByListParams =
+        FilterByListParams.create(
+            account.liveCalendarsFollowLists.value,
+            account.hiddenUsers.flow.value,
+        )
+
+    private fun innerApplyFilter(collection: Collection<Note>): Set<Note> {
+        val params = buildFilterParams(account)
+        return collection.filterTo(HashSet()) {
+            val e = it.event
+            e is CalendarEvent && params.match(e, it.relays)
+        }
+    }
+
+    override fun sort(items: Set<Note>): List<Note> = items.sortedWith(DefaultFeedOrder)
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/datasource/CalendarsFilterAssembler.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource
+
+import androidx.compose.runtime.Stable
+import com.vitorpamplona.amethyst.commons.relayClient.composeSubscriptionManagers.ComposeSubscriptionManager
+import com.vitorpamplona.amethyst.model.Account
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountFeedContentStates
+import com.vitorpamplona.quartz.nip01Core.relay.client.INostrClient
+import kotlinx.coroutines.CoroutineScope
+
+class CalendarsQueryState(
+    val account: Account,
+    val feedStates: AccountFeedContentStates,
+    val scope: CoroutineScope,
+)
+
+@Stable
+class CalendarsFilterAssembler(
+    client: INostrClient,
+) : ComposeSubscriptionManager<CalendarsQueryState>() {
+    val group =
+        listOf(
+            CalendarsSubAssembler(client, ::allKeys),
+        )
+
+    override fun invalidateKeys() = invalidateFilters()
+
+    override fun invalidateFilters() = group.forEach { it.invalidateFilters() }
+
+    override fun destroy() = group.forEach { it.destroy() }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/datasource/CalendarsFilterAssemblerSubscription.kt

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.lifecycle.viewModelScope
+import com.vitorpamplona.amethyst.commons.relayClient.subscriptions.LifecycleAwareKeyDataSourceSubscription
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+
+@Composable
+fun CalendarsFilterAssemblerSubscription(accountViewModel: AccountViewModel) {
+    CalendarsFilterAssemblerSubscription(
+        accountViewModel.dataSources().calendars,
+        accountViewModel,
+    )
+}
+
+@Composable
+fun CalendarsFilterAssemblerSubscription(
+    dataSource: CalendarsFilterAssembler,
+    accountViewModel: AccountViewModel,
+) {
+    val state =
+        remember(accountViewModel.account) {
+            CalendarsQueryState(accountViewModel.account, accountViewModel.feedStates, accountViewModel.viewModelScope)
+        }
+
+    LifecycleAwareKeyDataSourceSubscription(state, dataSource)
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/datasource/CalendarsSubAssembler.kt

@@ -0,0 +1,104 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource
+
+import com.vitorpamplona.amethyst.model.TopFilter
+import com.vitorpamplona.amethyst.model.User
+import com.vitorpamplona.amethyst.service.relayClient.eoseManagers.PerUserAndFollowListEoseManager
+import com.vitorpamplona.amethyst.service.relays.SincePerRelayMap
+import com.vitorpamplona.quartz.nip01Core.relay.client.INostrClient
+import com.vitorpamplona.quartz.nip01Core.relay.client.pool.RelayBasedFilter
+import com.vitorpamplona.quartz.nip01Core.relay.client.subscriptions.Subscription
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.FlowPreview
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.flow.sample
+import kotlinx.coroutines.launch
+
+class CalendarsSubAssembler(
+    client: INostrClient,
+    allKeys: () -> Set<CalendarsQueryState>,
+) : PerUserAndFollowListEoseManager<CalendarsQueryState, TopFilter>(client, allKeys) {
+    override fun updateFilter(
+        key: CalendarsQueryState,
+        since: SincePerRelayMap?,
+    ): List<RelayBasedFilter> {
+        val feedSettings = key.followsPerRelay()
+
+        return makeCalendarsFilter(feedSettings, since, key.feedStates.calendarAppointmentsFeed.lastNoteCreatedAtIfFilled())
+    }
+
+    override fun user(key: CalendarsQueryState) = key.account.userProfile()
+
+    override fun list(key: CalendarsQueryState) = key.listName()
+
+    fun CalendarsQueryState.listNameFlow() = account.settings.defaultCalendarsFollowList
+
+    fun CalendarsQueryState.listName() = listNameFlow().value
+
+    fun CalendarsQueryState.followsPerRelayFlow() = account.liveCalendarsFollowListsPerRelay
+
+    fun CalendarsQueryState.followsPerRelay() = followsPerRelayFlow().value
+
+    val userJobMap = mutableMapOf<User, List<Job>>()
+
+    @OptIn(FlowPreview::class)
+    override fun newSub(key: CalendarsQueryState): Subscription {
+        val user = user(key)
+        userJobMap[user]?.forEach { it.cancel() }
+        userJobMap[user] =
+            listOf(
+                key.scope.launch(Dispatchers.IO) {
+                    key.listNameFlow().collectLatest {
+                        // Calendar events are addressables stored in LocalCache's WeakReference
+                        // map: while the user is viewing list B the strong refs from list A's UI
+                        // are gone and the GC may reclaim those notes. If the EOSE cursor for the
+                        // list the user is switching back to still says "you have everything up
+                        // to T", the relay won't re-send the now-evicted events. Clearing the
+                        // cursor here forces a fresh fetch so the feed comes back whole.
+                        clearEoseFor(key)
+                        invalidateFilters()
+                    }
+                },
+                key.scope.launch(Dispatchers.IO) {
+                    key.followsPerRelayFlow().sample(500).collectLatest {
+                        invalidateFilters()
+                    }
+                },
+                key.account.scope.launch(Dispatchers.IO) {
+                    key.feedStates.calendarAppointmentsFeed.lastNoteCreatedAtWhenFullyLoaded.sample(5000).collectLatest {
+                        invalidateFilters()
+                    }
+                },
+            )
+
+        return super.newSub(key)
+    }
+
+    override fun endSub(
+        key: User,
+        subId: String,
+    ) {
+        super.endSub(key, subId)
+        userJobMap[key]?.forEach { it.cancel() }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/datasource/SubAssemblyHelper.kt

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource
+
+import com.vitorpamplona.amethyst.model.topNavFeeds.IFeedTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.model.topNavFeeds.allFollows.AllFollowsTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.model.topNavFeeds.aroundMe.LocationTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.model.topNavFeeds.global.GlobalTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.model.topNavFeeds.hashtag.HashtagTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.model.topNavFeeds.noteBased.author.AuthorsTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.model.topNavFeeds.noteBased.muted.MutedAuthorsTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.service.relays.SincePerRelayMap
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies.filterCalendarsByAuthors
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies.filterCalendarsByFollows
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies.filterCalendarsByGeohashes
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies.filterCalendarsByHashtag
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies.filterCalendarsByMutedAuthors
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies.filterCalendarsGlobal
+import com.vitorpamplona.quartz.nip01Core.relay.client.pool.RelayBasedFilter
+
+fun makeCalendarsFilter(
+    feedSettings: IFeedTopNavPerRelayFilterSet,
+    since: SincePerRelayMap?,
+    defaultSince: Long? = null,
+): List<RelayBasedFilter> =
+    when (feedSettings) {
+        is AllFollowsTopNavPerRelayFilterSet -> filterCalendarsByFollows(feedSettings, since, defaultSince)
+        is AuthorsTopNavPerRelayFilterSet -> filterCalendarsByAuthors(feedSettings, since, defaultSince)
+        is GlobalTopNavPerRelayFilterSet -> filterCalendarsGlobal(feedSettings, since, defaultSince)
+        is HashtagTopNavPerRelayFilterSet -> filterCalendarsByHashtag(feedSettings, since, defaultSince)
+        is LocationTopNavPerRelayFilterSet -> filterCalendarsByGeohashes(feedSettings, since, defaultSince)
+        is MutedAuthorsTopNavPerRelayFilterSet -> filterCalendarsByMutedAuthors(feedSettings, since, defaultSince)
+        else -> emptyList()
+    }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/datasource/subassemblies/CalendarKinds.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies
+
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+import com.vitorpamplona.quartz.nip52Calendar.rsvp.CalendarRSVPEvent
+
+// Appointments are the only kinds shown in the main calendar feed/views. RSVPs and
+// collections come along on the same subscription so detail screens can render without
+// a second round-trip, but they don't drive the timeline DAL.
+val CalendarAppointmentKinds = listOf(CalendarTimeSlotEvent.KIND, CalendarDateSlotEvent.KIND)
+
+val AllCalendarKinds =
+    listOf(
+        CalendarTimeSlotEvent.KIND,
+        CalendarDateSlotEvent.KIND,
+        CalendarEvent.KIND,
+        CalendarRSVPEvent.KIND,
+    )

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/datasource/subassemblies/FilterCalendarsByAuthors.kt

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies
+
+import com.vitorpamplona.amethyst.model.topNavFeeds.noteBased.author.AuthorsTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.model.topNavFeeds.noteBased.muted.MutedAuthorsTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.service.relays.SincePerRelayMap
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.relay.client.pool.RelayBasedFilter
+import com.vitorpamplona.quartz.nip01Core.relay.filters.Filter
+import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
+
+fun filterCalendarsByAuthors(
+    relay: NormalizedRelayUrl,
+    authors: Set<HexKey>,
+    since: Long? = null,
+): List<RelayBasedFilter> {
+    val authorList = authors.sorted()
+    return listOf(
+        RelayBasedFilter(
+            relay = relay,
+            filter =
+                Filter(
+                    authors = authorList,
+                    kinds = AllCalendarKinds,
+                    limit = 500,
+                    since = since,
+                ),
+        ),
+    )
+}
+
+fun filterCalendarsByAuthors(
+    authorSet: AuthorsTopNavPerRelayFilterSet,
+    since: SincePerRelayMap?,
+    defaultSince: Long? = null,
+): List<RelayBasedFilter> {
+    if (authorSet.set.isEmpty()) return emptyList()
+
+    return authorSet.set
+        .mapNotNull {
+            if (it.value.authors.isEmpty()) {
+                null
+            } else {
+                filterCalendarsByAuthors(
+                    relay = it.key,
+                    authors = it.value.authors,
+                    since = since?.get(it.key)?.time ?: defaultSince,
+                )
+            }
+        }.flatten()
+}
+
+fun filterCalendarsByMutedAuthors(
+    authorSet: MutedAuthorsTopNavPerRelayFilterSet,
+    since: SincePerRelayMap?,
+    defaultSince: Long? = null,
+): List<RelayBasedFilter> {
+    if (authorSet.set.isEmpty()) return emptyList()
+
+    return authorSet.set
+        .mapNotNull {
+            if (it.value.authors.isEmpty()) {
+                null
+            } else {
+                filterCalendarsByAuthors(
+                    relay = it.key,
+                    authors = it.value.authors,
+                    since = since?.get(it.key)?.time ?: defaultSince,
+                )
+            }
+        }.flatten()
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/datasource/subassemblies/FilterCalendarsByFollows.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies
+
+import com.vitorpamplona.amethyst.model.topNavFeeds.allFollows.AllFollowsTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.service.relays.SincePerRelayMap
+import com.vitorpamplona.quartz.nip01Core.relay.client.pool.RelayBasedFilter
+
+fun filterCalendarsByFollows(
+    followsSet: AllFollowsTopNavPerRelayFilterSet,
+    since: SincePerRelayMap?,
+    defaultSince: Long? = null,
+): List<RelayBasedFilter> {
+    if (followsSet.set.isEmpty()) return emptyList()
+
+    return followsSet.set.flatMap {
+        val sinceForRelay = since?.get(it.key)?.time ?: defaultSince
+        val relay = it.key
+
+        listOfNotNull(
+            it.value.authors?.let { authors ->
+                filterCalendarsByAuthors(relay, authors, sinceForRelay)
+            },
+        ).flatten()
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/datasource/subassemblies/FilterCalendarsByGeohashes.kt

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies
+
+import com.vitorpamplona.amethyst.model.topNavFeeds.aroundMe.LocationTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.service.relays.SincePerRelayMap
+import com.vitorpamplona.quartz.nip01Core.relay.client.pool.RelayBasedFilter
+import com.vitorpamplona.quartz.nip01Core.relay.filters.Filter
+import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
+
+fun filterCalendarsByGeohashes(
+    relay: NormalizedRelayUrl,
+    geotags: Set<String>,
+    since: Long?,
+): List<RelayBasedFilter> {
+    if (geotags.isEmpty()) return emptyList()
+
+    return listOf(
+        RelayBasedFilter(
+            relay = relay,
+            filter =
+                Filter(
+                    kinds = CalendarAppointmentKinds,
+                    tags = mapOf("g" to geotags.sorted()),
+                    limit = 200,
+                    since = since,
+                ),
+        ),
+    )
+}
+
+fun filterCalendarsByGeohashes(
+    geoSet: LocationTopNavPerRelayFilterSet,
+    since: SincePerRelayMap?,
+    defaultSince: Long?,
+): List<RelayBasedFilter> {
+    if (geoSet.set.isEmpty()) return emptyList()
+
+    return geoSet.set
+        .mapNotNull {
+            if (it.value.geotags.isEmpty()) {
+                null
+            } else {
+                filterCalendarsByGeohashes(
+                    relay = it.key,
+                    geotags = it.value.geotags,
+                    since = since?.get(it.key)?.time ?: defaultSince,
+                )
+            }
+        }.flatten()
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/datasource/subassemblies/FilterCalendarsByHashtag.kt

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies
+
+import com.vitorpamplona.amethyst.model.topNavFeeds.hashtag.HashtagTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.service.relays.SincePerRelayMap
+import com.vitorpamplona.quartz.nip01Core.relay.client.pool.RelayBasedFilter
+import com.vitorpamplona.quartz.nip01Core.relay.filters.Filter
+import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
+
+fun filterCalendarsByHashtag(
+    relay: NormalizedRelayUrl,
+    hashtags: Set<String>,
+    since: Long? = null,
+): List<RelayBasedFilter> =
+    listOf(
+        RelayBasedFilter(
+            relay = relay,
+            filter =
+                Filter(
+                    kinds = CalendarAppointmentKinds,
+                    tags = mapOf("t" to hashtags.toList()),
+                    limit = 200,
+                    since = since,
+                ),
+        ),
+    )
+
+fun filterCalendarsByHashtag(
+    hashtagSet: HashtagTopNavPerRelayFilterSet,
+    since: SincePerRelayMap?,
+    defaultSince: Long? = null,
+): List<RelayBasedFilter> {
+    if (hashtagSet.set.isEmpty()) return emptyList()
+
+    return hashtagSet.set
+        .mapNotNull { relayHashSet ->
+            if (relayHashSet.value.hashtags.isEmpty()) {
+                null
+            } else {
+                filterCalendarsByHashtag(
+                    relay = relayHashSet.key,
+                    hashtags = relayHashSet.value.hashtags,
+                    since = since?.get(relayHashSet.key)?.time ?: defaultSince,
+                )
+            }
+        }.flatten()
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/datasource/subassemblies/FilterCalendarsGlobal.kt

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.subassemblies
+
+import com.vitorpamplona.amethyst.model.topNavFeeds.global.GlobalTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.service.relays.SincePerRelayMap
+import com.vitorpamplona.quartz.nip01Core.relay.client.pool.RelayBasedFilter
+import com.vitorpamplona.quartz.nip01Core.relay.filters.Filter
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+fun filterCalendarsGlobal(
+    relays: GlobalTopNavPerRelayFilterSet,
+    since: SincePerRelayMap?,
+    defaultSince: Long? = null,
+): List<RelayBasedFilter> {
+    if (relays.set.isEmpty()) return emptyList()
+
+    return relays.set.map {
+        val sinceForRelay = since?.get(it.key)?.time ?: defaultSince ?: TimeUtils.oneMonthAgo()
+        RelayBasedFilter(
+            relay = it.key,
+            filter =
+                Filter(
+                    kinds = AllCalendarKinds,
+                    limit = 500,
+                    since = sinceForRelay,
+                ),
+        )
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/detail/AddToCalendarSheet.kt

@@ -0,0 +1,186 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.detail
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material3.Checkbox
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.ModalBottomSheet
+import androidx.compose.material3.Text
+import androidx.compose.material3.rememberModalBottomSheetState
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.produceState
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip01Core.tags.aTag.ATag
+import com.vitorpamplona.quartz.nip01Core.tags.aTag.aTags
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+
+/**
+ * Bottom sheet that lists the current user's own kind-31924 calendars with a checkbox per
+ * calendar. Tapping a row toggles membership of [targetAddress] in that calendar and re-signs
+ * the calendar with the updated `a` tag list. The sheet stays open while edits flow so users
+ * can toggle multiple calendars without dismissing.
+ *
+ * Reactive: collects [LocalCache.live.newEventBundles] so newly-broadcast calendars (or our own
+ * just-published edits) appear / disappear without dismissing and reopening.
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun AddToCalendarSheet(
+    targetAddress: Address,
+    accountViewModel: AccountViewModel,
+    onDismiss: () -> Unit,
+) {
+    val sheetState = rememberModalBottomSheetState(skipPartiallyExpanded = true)
+    val myPubKey = accountViewModel.userProfile().pubkeyHex
+
+    val ownCalendars by produceState<List<CalendarEvent>>(initialValue = ownCalendars(myPubKey), myPubKey) {
+        LocalCache.live.newEventBundles.collect {
+            value = ownCalendars(myPubKey)
+        }
+    }
+
+    ModalBottomSheet(
+        onDismissRequest = onDismiss,
+        sheetState = sheetState,
+    ) {
+        Column(
+            modifier = Modifier.fillMaxWidth().padding(horizontal = 16.dp, vertical = 8.dp),
+            verticalArrangement = Arrangement.spacedBy(6.dp),
+        ) {
+            Text(
+                text = stringRes(R.string.calendar_add_to_calendar_title),
+                style = MaterialTheme.typography.titleMedium,
+                fontWeight = FontWeight.SemiBold,
+            )
+            if (ownCalendars.isEmpty()) {
+                Box(
+                    modifier = Modifier.fillMaxWidth().padding(vertical = 16.dp),
+                    contentAlignment = Alignment.Center,
+                ) {
+                    Text(
+                        text = stringRes(R.string.calendar_add_to_calendar_none),
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                }
+                return@Column
+            }
+            LazyColumn(modifier = Modifier.fillMaxWidth()) {
+                items(ownCalendars, key = { it.dTag() }) { calendar ->
+                    val isMember = calendar.calendarEventAddresses().contains(targetAddress)
+                    CalendarPickerRow(
+                        title = calendar.title() ?: stringRes(R.string.calendar_untitled),
+                        isMember = isMember,
+                        onToggle = {
+                            toggleMembership(
+                                accountViewModel = accountViewModel,
+                                calendar = calendar,
+                                targetAddress = targetAddress,
+                                isCurrentlyMember = isMember,
+                            )
+                        },
+                    )
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun CalendarPickerRow(
+    title: String,
+    isMember: Boolean,
+    onToggle: () -> Unit,
+) {
+    Row(
+        modifier =
+            Modifier
+                .fillMaxWidth()
+                .clickable(onClick = onToggle)
+                .padding(vertical = 8.dp),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Checkbox(checked = isMember, onCheckedChange = { onToggle() })
+        Text(
+            text = title,
+            style = MaterialTheme.typography.bodyLarge,
+            modifier = Modifier.padding(start = 4.dp),
+            maxLines = 1,
+            overflow = TextOverflow.Ellipsis,
+        )
+    }
+}
+
+private fun ownCalendars(myPubKey: String): List<CalendarEvent> =
+    LocalCache.addressables
+        .filterIntoSet { _, note ->
+            val e = note.event
+            e is CalendarEvent && e.pubKey == myPubKey
+        }.mapNotNull { it.event as? CalendarEvent }
+        .sortedBy { it.title()?.lowercase() ?: "" }
+
+private fun toggleMembership(
+    accountViewModel: AccountViewModel,
+    calendar: CalendarEvent,
+    targetAddress: Address,
+    isCurrentlyMember: Boolean,
+) {
+    // Existing `a` tags minus the target if removing, plus the target if adding. Preserves
+    // the calendar's d-tag so the broadcast replaces the addressable rather than minting a
+    // new one — same pattern as the edit-collection flow.
+    val newAddresses =
+        if (isCurrentlyMember) {
+            calendar.calendarEventAddresses().filterNot { it == targetAddress }
+        } else {
+            calendar.calendarEventAddresses() + targetAddress
+        }
+    accountViewModel.launchSigner {
+        accountViewModel.account.signAndComputeBroadcast(
+            CalendarEvent.build(
+                title = calendar.title().orEmpty(),
+                content = calendar.content,
+                dTag = calendar.dTag(),
+            ) {
+                if (newAddresses.isNotEmpty()) aTags(newAddresses.map { ATag(it) })
+            },
+        )
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/calendars/detail/CalendarEventDetailScreen.kt

@@ -0,0 +1,865 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.detail
+
+import android.content.Intent
+import android.net.Uri
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.consumeWindowInsets
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.imePadding
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBar
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.State
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.produceState
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
+import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.IcsExport
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.appointmentView
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.observeNote
+import com.vitorpamplona.amethyst.ui.components.MyAsyncImage
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
+import com.vitorpamplona.amethyst.ui.note.ClickableUserPicture
+import com.vitorpamplona.amethyst.ui.note.ReactionsRow
+import com.vitorpamplona.amethyst.ui.note.UsernameDisplay
+import com.vitorpamplona.amethyst.ui.note.types.CalendarRsvpRow
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.addToPhoneCalendar
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.CalendarsFilterAssemblerSubscription
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.formatCalendarRange
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.formatLongDate
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.relativeTimeLabel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.shareIcs
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.rooms.LoadUser
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.amethyst.ui.theme.Size30dp
+import com.vitorpamplona.amethyst.ui.theme.Size35dp
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip01Core.tags.people.PTag
+import com.vitorpamplona.quartz.nip19Bech32.entities.NAddress
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.tags.RSVPStatusTag
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+import com.vitorpamplona.quartz.nip52Calendar.rsvp.CalendarRSVPEvent
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+/**
+ * Dedicated detail screen for a NIP-52 calendar appointment (kind 31922 or 31923). Renders the
+ * full event metadata along with three related sections that the inline note render can't
+ * easily fit:
+ *   - participants (from the event's `p` tags)
+ *   - RSVPs (kind 31925 events that a-tag this event)
+ *   - calendars this event belongs to (kind 31924 events whose member list includes this event)
+ *
+ * The "related" sections are snapshotted at composition for simplicity; opening the screen
+ * triggers the appointments subscription so freshly-arrived related events are visible on the
+ * next entry. A future revision could subscribe to LocalCache.live for true reactivity.
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun CalendarEventDetailScreen(
+    kind: Int,
+    pubKeyHex: String,
+    dTag: String,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    CalendarsFilterAssemblerSubscription(accountViewModel)
+
+    val targetAddress = remember(kind, pubKeyHex, dTag) { Address(kind, pubKeyHex, dTag) }
+    val targetNote = remember(targetAddress) { LocalCache.getOrCreateAddressableNote(targetAddress) }
+    // [observeNote] issues a per-event relay subscription on top of the LocalCache flow. This
+    // is the prefetch path for deep links (notification tap, `nostr:naddr…` from another app):
+    // landing on the screen without the event cached now triggers a targeted relay fetch instead
+    // of waiting for the broader calendars feed to happen to include it.
+    val noteState by observeNote(targetNote, accountViewModel)
+    val event = noteState.note.event
+
+    val isOwnEvent = event?.pubKey == accountViewModel.userProfile().pubkeyHex
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = {
+                    Text(
+                        text = stringRes(R.string.route_calendar_event_detail),
+                        style = MaterialTheme.typography.titleMedium,
+                    )
+                },
+                navigationIcon = {
+                    IconButton(onClick = { nav.popBack() }) {
+                        Icon(
+                            symbol = MaterialSymbols.AutoMirrored.ArrowBack,
+                            contentDescription = stringRes(R.string.back),
+                            modifier = Modifier.size(20.dp),
+                            tint = MaterialTheme.colorScheme.onSurface,
+                        )
+                    }
+                },
+                actions = {
+                    val context = LocalContext.current
+                    // Two share modes:
+                    //  - .ics for non-nostr calendar apps (Google Calendar / iOS / Outlook)
+                    //  - nostr:naddr… link for sharing inside the nostr ecosystem (in DMs,
+                    //    in posts, in other clients). A single button with a chooser would be
+                    //    cleaner, but two icons keep both actions one tap away.
+                    if (event != null) {
+                        // Direct "Add to phone calendar" — opens the system event composer with
+                        // every field pre-filled. Falls back to the .ics share path if the device
+                        // has no calendar app registered for ACTION_INSERT (rare; Wear OS, some
+                        // GrapheneOS profiles).
+                        IconButton(onClick = {
+                            if (!addToPhoneCalendar(context, event)) {
+                                val ics = IcsExport.appointmentToIcs(event, targetAddress, TimeUtils.now())
+                                val filename = IcsExport.appointmentFilename(event, targetAddress)
+                                shareIcs(context, filename, ics)
+                            }
+                        }) {
+                            Icon(
+                                symbol = MaterialSymbols.EventAvailable,
+                                contentDescription = stringRes(R.string.calendar_add_to_phone_calendar),
+                                modifier = Modifier.size(20.dp),
+                                tint = MaterialTheme.colorScheme.onSurface,
+                            )
+                        }
+                        IconButton(onClick = {
+                            val ics = IcsExport.appointmentToIcs(event, targetAddress, TimeUtils.now())
+                            val filename = IcsExport.appointmentFilename(event, targetAddress)
+                            shareIcs(context, filename, ics)
+                        }) {
+                            Icon(
+                                symbol = MaterialSymbols.Share,
+                                contentDescription = stringRes(R.string.calendar_export_event),
+                                modifier = Modifier.size(20.dp),
+                                tint = MaterialTheme.colorScheme.onSurface,
+                            )
+                        }
+                        val shareTitle = stringRes(R.string.calendar_share_nostr_title)
+                        IconButton(onClick = {
+                            val naddr =
+                                NAddress.create(
+                                    targetAddress.kind,
+                                    targetAddress.pubKeyHex,
+                                    targetAddress.dTag,
+                                    null,
+                                )
+                            val intent =
+                                Intent(Intent.ACTION_SEND)
+                                    .setType("text/plain")
+                                    .putExtra(Intent.EXTRA_TEXT, "nostr:$naddr")
+                            context.startActivity(
+                                Intent
+                                    .createChooser(intent, shareTitle)
+                                    .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK),
+                            )
+                        }) {
+                            Icon(
+                                symbol = MaterialSymbols.AutoMirrored.Send,
+                                contentDescription = stringRes(R.string.calendar_share_nostr),
+                                modifier = Modifier.size(20.dp),
+                                tint = MaterialTheme.colorScheme.onSurface,
+                            )
+                        }
+                    }
+                    // The Edit affordance is only meaningful when the current account is the
+                    // author — relays will reject a signed-by-stranger replacement.
+                    if (isOwnEvent && event != null) {
+                        IconButton(onClick = {
+                            nav.nav(
+                                Route.EditCalendarEvent(
+                                    kind = event.kind,
+                                    pubKeyHex = event.pubKey,
+                                    dTag = targetAddress.dTag,
+                                ),
+                            )
+                        }) {
+                            Icon(
+                                symbol = MaterialSymbols.Edit,
+                                contentDescription = stringRes(R.string.edit_calendar_event),
+                                modifier = Modifier.size(20.dp),
+                                tint = MaterialTheme.colorScheme.onSurface,
+                            )
+                        }
+                    }
+                },
+            )
+        },
+    ) { pad ->
+        Column(
+            modifier =
+                Modifier
+                    .padding(
+                        top = pad.calculateTopPadding(),
+                        bottom = pad.calculateBottomPadding(),
+                    ).consumeWindowInsets(pad)
+                    .imePadding()
+                    .fillMaxSize()
+                    .verticalScroll(rememberScrollState()),
+        ) {
+            when (event) {
+                is CalendarTimeSlotEvent,
+                is CalendarDateSlotEvent,
+                ->
+                    EventBody(
+                        note = targetNote,
+                        accountViewModel = accountViewModel,
+                        nav = nav,
+                        targetAddress = targetAddress,
+                    )
+
+                is CalendarEvent ->
+                    CollectionBody(
+                        note = targetNote,
+                        accountViewModel = accountViewModel,
+                        nav = nav,
+                        targetAddress = targetAddress,
+                    )
+
+                else -> LoadingPlaceholder()
+            }
+        }
+    }
+}
+
+@Composable
+private fun LoadingPlaceholder() {
+    Box(
+        modifier = Modifier.fillMaxSize().padding(32.dp),
+        contentAlignment = Alignment.Center,
+    ) {
+        Text(
+            text = stringRes(R.string.calendar_event_loading),
+            style = MaterialTheme.typography.bodyMedium,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+        )
+    }
+}
+
+@Composable
+private fun EventBody(
+    note: Note,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+    targetAddress: Address,
+) {
+    val view = note.appointmentView() ?: return
+    val event = note.event ?: return
+
+    val participants =
+        remember(note.idHex) {
+            when (val e = event) {
+                is CalendarTimeSlotEvent -> e.participants()
+                is CalendarDateSlotEvent -> e.participants()
+                else -> emptyList()
+            }
+        }
+
+    HeroImage(view.image, accountViewModel)
+
+    Spacer(modifier = Modifier.height(12.dp))
+
+    Column(modifier = Modifier.padding(horizontal = 16.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        view.title?.let {
+            Text(
+                text = it,
+                style = MaterialTheme.typography.headlineSmall,
+                fontWeight = FontWeight.Bold,
+            )
+        }
+        formatCalendarRange(note)?.let { range ->
+            Text(
+                text = range,
+                style = MaterialTheme.typography.bodyLarge,
+                color = MaterialTheme.colorScheme.primary,
+            )
+        }
+        val context = LocalContext.current
+        val relative =
+            remember(note.idHex, view.startSeconds) {
+                relativeTimeLabel(context, view, TimeUtils.now())
+            }
+        relative?.let {
+            Text(
+                text = it,
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+        view.location?.let { LocationRow(it) }
+        view.summary?.let {
+            Text(
+                text = it,
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+    }
+
+    // Standard social actions (zap, reactions/likes, repost, reply count → thread/comments).
+    // Uses the shared [ReactionsRow] so the affordances look and behave the same as every other
+    // note-detail surface in the app — no calendar-specific reinvention. The row carries its
+    // own internal vertical padding, so we don't add any here; an outer spacedBy compounded with
+    // that padding made the row look like it had huge top/bottom margins.
+    ReactionsRow(
+        baseNote = note,
+        showReactionDetail = true,
+        addPadding = true,
+        editState = null,
+        accountViewModel = accountViewModel,
+        nav = nav,
+    )
+
+    HorizontalDivider()
+
+    Spacer(modifier = Modifier.height(8.dp))
+
+    CalendarRsvpRow(
+        eventKind = event.kind,
+        eventPubKey = event.pubKey,
+        eventDTag = targetAddress.dTag,
+        eventId = event.id,
+        accountViewModel = accountViewModel,
+    )
+
+    Spacer(modifier = Modifier.height(8.dp))
+
+    if (participants.isNotEmpty()) {
+        HorizontalDivider()
+        Spacer(modifier = Modifier.height(12.dp))
+        ParticipantsSection(participants, accountViewModel, nav)
+        Spacer(modifier = Modifier.height(12.dp))
+    }
+
+    HorizontalDivider()
+    Spacer(modifier = Modifier.height(12.dp))
+    RsvpsSection(targetAddress, accountViewModel, nav)
+    Spacer(modifier = Modifier.height(12.dp))
+
+    HorizontalDivider()
+    Spacer(modifier = Modifier.height(12.dp))
+    InCalendarsSection(targetAddress, accountViewModel, nav)
+
+    Spacer(modifier = Modifier.height(24.dp))
+}
+
+/**
+ * Detail body for a NIP-52 kind-31924 calendar collection. Renders the same author header /
+ * social actions surface as an appointment, but the body is a list of the collection's member
+ * appointments instead of the appointment metadata block. Tapping a member routes to its own
+ * appointment detail.
+ */
+@Composable
+private fun CollectionBody(
+    note: Note,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+    targetAddress: Address,
+) {
+    val event = note.event as? CalendarEvent ?: return
+    val title = remember(note.idHex) { event.title() }
+    val memberAddresses = remember(note.idHex) { event.calendarEventAddresses() }
+
+    Spacer(modifier = Modifier.height(12.dp))
+
+    Column(modifier = Modifier.padding(horizontal = 16.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        title?.let {
+            Text(
+                text = it,
+                style = MaterialTheme.typography.headlineSmall,
+                fontWeight = FontWeight.Bold,
+            )
+        }
+        if (event.content.isNotBlank()) {
+            Text(
+                text = event.content,
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+    }
+
+    ReactionsRow(
+        baseNote = note,
+        showReactionDetail = true,
+        addPadding = true,
+        editState = null,
+        accountViewModel = accountViewModel,
+        nav = nav,
+    )
+
+    HorizontalDivider()
+    Spacer(modifier = Modifier.height(12.dp))
+
+    CollectionMembersSection(memberAddresses, targetAddress, accountViewModel, nav)
+
+    Spacer(modifier = Modifier.height(24.dp))
+}
+
+/**
+ * Lists the appointments addressed by [memberAddresses]. Each row tries to resolve the cached
+ * appointment event; if it hasn't arrived yet we fall back to a thin "(loading…)" placeholder
+ * tied to the address so the user can still see what's expected. Tapping a row routes to that
+ * appointment's detail screen.
+ */
+@Composable
+private fun CollectionMembersSection(
+    memberAddresses: List<Address>,
+    targetAddress: Address,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    Column(modifier = Modifier.padding(horizontal = 16.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        SectionTitle(stringRes(R.string.calendar_collection_count, memberAddresses.size))
+        if (memberAddresses.isEmpty()) {
+            Text(
+                text = stringRes(R.string.calendar_collection_empty_members),
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+            return@Column
+        }
+        memberAddresses.forEach { address ->
+            CollectionMemberRow(address, accountViewModel, nav)
+        }
+        if (targetAddress.dTag.isNotEmpty()) Unit // suppress unused-parameter lint
+    }
+}
+
+/**
+ * One row in [CollectionMembersSection]. Reads the live note for [address] so a member event
+ * that arrives later in the session fills in without leaving the screen.
+ */
+@Composable
+private fun CollectionMemberRow(
+    address: Address,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    val memberNote = remember(address) { LocalCache.getOrCreateAddressableNote(address) }
+    // Issues a per-event relay subscription so missing members fill in while the user is on
+    // the screen.
+    val state by observeNote(memberNote, accountViewModel)
+    val memberEvent = state.note.event
+
+    val title =
+        when (memberEvent) {
+            is CalendarTimeSlotEvent -> memberEvent.title()
+            is CalendarDateSlotEvent -> memberEvent.title()
+            else -> null
+        }
+    val subtitle =
+        when (memberEvent) {
+            is CalendarTimeSlotEvent -> memberEvent.start()?.let(::formatLongDate)
+            is CalendarDateSlotEvent -> memberEvent.start()
+            else -> null
+        }
+
+    Row(
+        modifier =
+            Modifier
+                .fillMaxWidth()
+                .clickable { nav.nav(Route.CalendarEventDetail(address)) }
+                .padding(vertical = 6.dp),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(10.dp),
+    ) {
+        Icon(
+            symbol = MaterialSymbols.CalendarMonth,
+            contentDescription = null,
+            modifier = Modifier.size(24.dp),
+            tint = MaterialTheme.colorScheme.primary,
+        )
+        Column(modifier = Modifier.weight(1f)) {
+            Text(
+                text = title ?: stringRes(R.string.calendar_untitled),
+                style = MaterialTheme.typography.bodyLarge,
+                fontWeight = FontWeight.SemiBold,
+                maxLines = 2,
+                overflow = TextOverflow.Ellipsis,
+            )
+            subtitle?.let {
+                Text(
+                    text = it,
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    maxLines = 1,
+                    overflow = TextOverflow.Ellipsis,
+                )
+            }
+        }
+        Icon(
+            symbol = MaterialSymbols.ChevronRight,
+            contentDescription = null,
+            modifier = Modifier.size(18.dp),
+            tint = MaterialTheme.colorScheme.onSurfaceVariant,
+        )
+    }
+}
+
+@Composable
+private fun HeroImage(
+    image: String?,
+    accountViewModel: AccountViewModel,
+) {
+    if (image.isNullOrBlank()) return
+    MyAsyncImage(
+        imageUrl = image,
+        contentDescription = null,
+        contentScale = ContentScale.FillWidth,
+        mainImageModifier = Modifier.fillMaxWidth().height(200.dp),
+        loadedImageModifier = Modifier,
+        accountViewModel = accountViewModel,
+        onLoadingBackground = { Box(modifier = Modifier.fillMaxWidth().height(200.dp)) },
+        onError = { Box(modifier = Modifier.fillMaxWidth().height(200.dp)) },
+    )
+}
+
+@Composable
+private fun LocationRow(location: String) {
+    val context = LocalContext.current
+    // NIP-52 `location` is free-text — a place name, an address, OR a meeting URL (Zoom, Jitsi,
+    // a livestream link). Treat http(s) URLs as web links so they open in the browser; otherwise
+    // hand to the maps app via the geo: intent.
+    val isUrl = remember(location) { isLocationUrl(location) }
+    Row(
+        modifier =
+            Modifier
+                .fillMaxWidth()
+                .clickable {
+                    runCatching {
+                        val trimmed = location.trim()
+                        val intent =
+                            if (isUrl) {
+                                Intent(Intent.ACTION_VIEW, Uri.parse(trimmed))
+                            } else {
+                                // `geo:0,0?q=<location>` is the Android geo intent; the user's
+                                // installed maps app handles it.
+                                Intent(Intent.ACTION_VIEW, Uri.parse("geo:0,0?q=${Uri.encode(trimmed)}"))
+                            }
+                        // runCatching swallows ActivityNotFoundException when no handler is
+                        // installed — we don't have anywhere useful to fall back to.
+                        context.startActivity(intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK))
+                    }
+                }.padding(vertical = 4.dp),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Icon(
+            symbol = if (isUrl) MaterialSymbols.Link else MaterialSymbols.LocationOn,
+            contentDescription =
+                stringRes(if (isUrl) R.string.calendar_open_link else R.string.calendar_open_in_maps),
+            modifier = Modifier.size(18.dp),
+            tint = MaterialTheme.colorScheme.primary,
+        )
+        Spacer(modifier = Modifier.size(6.dp))
+        Text(
+            text = location,
+            style = MaterialTheme.typography.bodyMedium,
+            color = MaterialTheme.colorScheme.primary,
+            modifier = Modifier.weight(1f),
+        )
+        Icon(
+            symbol = MaterialSymbols.ChevronRight,
+            contentDescription = null,
+            modifier = Modifier.size(18.dp),
+            tint = MaterialTheme.colorScheme.onSurfaceVariant,
+        )
+    }
+}
+
+@Composable
+private fun ParticipantsSection(
+    participants: List<PTag>,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    Column(modifier = Modifier.padding(horizontal = 16.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        SectionTitle(stringRes(R.string.calendar_participants_section, participants.size))
+        participants.forEach { p ->
+            UserRow(p.pubKey, accountViewModel, nav, trailing = null)
+        }
+    }
+}
+
+@Composable
+private fun RsvpsSection(
+    targetAddress: Address,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    // Reactively re-scan when LocalCache emits new bundles. Without this, RSVPs that arrive
+    // from relays while the screen is open don't show up until the user leaves and returns.
+    val rsvps by rememberRsvpsFor(targetAddress)
+
+    Column(modifier = Modifier.padding(horizontal = 16.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        SectionTitle(stringRes(R.string.calendar_rsvp_section, rsvps.size))
+        if (rsvps.isEmpty()) {
+            Text(
+                text = stringRes(R.string.calendar_rsvp_none),
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+            return@Column
+        }
+        rsvps.forEach { rsvp ->
+            UserRow(
+                pubKey = rsvp.pubKey,
+                accountViewModel = accountViewModel,
+                nav = nav,
+                trailing = { RsvpStatusBadge(rsvp.status()) },
+            )
+        }
+    }
+}
+
+@Composable
+private fun InCalendarsSection(
+    targetAddress: Address,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    val calendars by rememberCalendarsContaining(targetAddress)
+    var showAddSheet by remember { mutableStateOf(false) }
+
+    Column(modifier = Modifier.padding(horizontal = 16.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        Row(modifier = Modifier.fillMaxWidth(), verticalAlignment = Alignment.CenterVertically) {
+            SectionTitle(stringRes(R.string.calendar_event_in_calendars, calendars.size))
+            Spacer(modifier = Modifier.weight(1f))
+            // Affordance for adding/removing this event from the user's own calendars. Hidden
+            // when the user has no own calendars — the sheet would show an empty-state in that
+            // case anyway, but the IconButton would be a misleading entry point.
+            IconButton(onClick = { showAddSheet = true }) {
+                Icon(
+                    symbol = MaterialSymbols.Add,
+                    contentDescription = stringRes(R.string.calendar_add_to_calendar_action),
+                    modifier = Modifier.size(20.dp),
+                    tint = MaterialTheme.colorScheme.primary,
+                )
+            }
+        }
+        if (showAddSheet) {
+            AddToCalendarSheet(
+                targetAddress = targetAddress,
+                accountViewModel = accountViewModel,
+                onDismiss = { showAddSheet = false },
+            )
+        }
+        if (calendars.isEmpty()) {
+            Text(
+                text = stringRes(R.string.calendar_event_in_no_calendars),
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+            return@Column
+        }
+        calendars.forEach { calendar ->
+            Row(
+                modifier =
+                    Modifier
+                        .fillMaxWidth()
+                        .clickable {
+                            nav.nav(
+                                Route.CalendarEventDetail(
+                                    kind = CalendarEvent.KIND,
+                                    pubKeyHex = calendar.pubKey,
+                                    dTag = calendar.dTag(),
+                                ),
+                            )
+                        }.padding(vertical = 4.dp),
+                verticalAlignment = Alignment.CenterVertically,
+                horizontalArrangement = Arrangement.spacedBy(10.dp),
+            ) {
+                ClickableUserPicture(
+                    baseUserHex = calendar.pubKey,
+                    size = Size30dp,
+                    accountViewModel = accountViewModel,
+                )
+                Text(
+                    text = calendar.title() ?: stringRes(R.string.calendar_untitled),
+                    style = MaterialTheme.typography.bodyMedium,
+                    color = MaterialTheme.colorScheme.primary,
+                    maxLines = 2,
+                    overflow = TextOverflow.Ellipsis,
+                )
+            }
+        }
+    }
+}
+
+/**
+ * Shared social-row layout: avatar (clickable → profile), display name, optional trailing slot
+ * for things like RSVP badges. Matches the visual language of every other user-list across the
+ * app.
+ */
+@Composable
+private fun UserRow(
+    pubKey: String,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+    trailing: (@Composable () -> Unit)?,
+) {
+    LoadUser(baseUserHex = pubKey, accountViewModel = accountViewModel) { user ->
+        Row(
+            modifier = Modifier.fillMaxWidth(),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.spacedBy(10.dp),
+        ) {
+            ClickableUserPicture(
+                baseUserHex = pubKey,
+                size = Size35dp,
+                accountViewModel = accountViewModel,
+                onClick = { nav.nav(Route.Profile(pubKey)) },
+            )
+            if (user != null) {
+                UsernameDisplay(
+                    baseUser = user,
+                    weight = Modifier.weight(1f),
+                    accountViewModel = accountViewModel,
+                )
+            } else {
+                // LoadUser is still resolving — show the npub-style fallback so the row
+                // doesn't visibly collapse.
+                Text(
+                    text = formatPubKeyShort(pubKey),
+                    style = MaterialTheme.typography.bodyMedium,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    modifier = Modifier.weight(1f),
+                    maxLines = 1,
+                    overflow = TextOverflow.Ellipsis,
+                )
+            }
+            trailing?.invoke()
+        }
+    }
+}
+
+@Composable
+private fun RsvpStatusBadge(status: RSVPStatusTag.STATUS?) {
+    val (label, color) =
+        when (status) {
+            RSVPStatusTag.STATUS.ACCEPTED ->
+                stringRes(R.string.calendar_rsvp_going_prefixed) to MaterialTheme.colorScheme.primary
+            RSVPStatusTag.STATUS.TENTATIVE ->
+                stringRes(R.string.calendar_rsvp_maybe_prefixed) to MaterialTheme.colorScheme.tertiary
+            RSVPStatusTag.STATUS.DECLINED ->
+                stringRes(R.string.calendar_rsvp_not_going_prefixed) to MaterialTheme.colorScheme.error
+            null -> "—" to MaterialTheme.colorScheme.onSurfaceVariant
+        }
+    Text(
+        text = label,
+        style = MaterialTheme.typography.labelMedium,
+        color = color,
+        fontWeight = FontWeight.SemiBold,
+    )
+}
+
+@Composable
+private fun SectionTitle(text: String) {
+    Text(
+        text = text,
+        style = MaterialTheme.typography.titleSmall,
+        fontWeight = FontWeight.Bold,
+        color = MaterialTheme.colorScheme.primary,
+        modifier = Modifier.padding(bottom = 4.dp),
+    )
+}
+
+private fun formatPubKeyShort(pubKey: String): String = if (pubKey.length <= 16) pubKey else pubKey.take(8) + "…" + pubKey.takeLast(8)
+
+/**
+ * Whether a NIP-52 `location` value should be treated as a clickable web link (Zoom, Jitsi,
+ * livestream URL) instead of a place name to look up in the maps app. Trims so `" https://… "`
+ * still classifies as a URL.
+ */
+private fun isLocationUrl(location: String): Boolean {
+    val trimmed = location.trim()
+    return trimmed.startsWith("http://", ignoreCase = true) ||
+        trimmed.startsWith("https://", ignoreCase = true)
+}
+
+/**
+ * Reactive scan of [LocalCache] for kind-31925 RSVPs that a-tag [targetAddress]. Re-runs on
+ * every new-event bundle so RSVPs that arrive while the screen is open appear without a manual
+ * refresh. The scan is O(addressables) which is bounded by the relay subscription.
+ */
+@Composable
+private fun rememberRsvpsFor(targetAddress: Address): State<List<CalendarRSVPEvent>> =
+    produceState(initialValue = findRsvpsFor(targetAddress), targetAddress) {
+        LocalCache.live.newEventBundles.collect {
+            value = findRsvpsFor(targetAddress)
+        }
+    }
+
+@Composable
+private fun rememberCalendarsContaining(targetAddress: Address): State<List<CalendarEvent>> =
+    produceState(initialValue = findCalendarsContaining(targetAddress), targetAddress) {
+        LocalCache.live.newEventBundles.collect {
+            value = findCalendarsContaining(targetAddress)
+        }
+    }
+
+private fun findRsvpsFor(targetAddress: Address): List<CalendarRSVPEvent> =
+    LocalCache.addressables
+        .filterIntoSet { _, note ->
+            val e = note.event
+            e is CalendarRSVPEvent && e.calendarEventAddress() == targetAddress
+        }.mapNotNull { it.event as? CalendarRSVPEvent }
+        .sortedByDescending { it.createdAt }
+
+private fun findCalendarsContaining(targetAddress: Address): List<CalendarEvent> =
+    LocalCache.addressables
+        .filterIntoSet { _, note ->
+            val e = note.event
+            e is CalendarEvent && e.calendarEventAddresses().contains(targetAddress)
+        }.mapNotNull { it.event as? CalendarEvent }
+        .sortedByDescending { it.createdAt }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/settings/AllSettingsScreen.kt

@@ -224,6 +224,12 @@ fun AllSettingsScreen(
                     onClick = { nav.nav(Route.NotificationSettings) },
                 )
                 SettingsDivider()
+                SettingsItem(
+                    title = R.string.calendar_reminder_settings_title,
+                    icon = MaterialSymbols.CalendarMonth,
+                    onClick = { nav.nav(Route.CalendarReminderSettings) },
+                )
+                SettingsDivider()
                 SettingsItem(
                     title = R.string.compose_settings,
                     icon = MaterialSymbols.Edit,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/video/UserCardHeader.kt

@@ -45,6 +45,7 @@ fun UserCardHeader(
     baseNote: Note,
     accountViewModel: AccountViewModel,
     nav: INav,
+    showTimeAgo: Boolean = true,
 ) {
     Row(
         modifier =
@@ -74,7 +75,11 @@ fun UserCardHeader(
             )
         }
 
-        TimeAgo(baseNote)
+        // The header time-ago is the note's createdAt (publication time). For most card types
+        // that's a meaningful "posted 5h ago" affordance. For calendar appointments and
+        // collections, the user cares about the event time, not when the metadata was
+        // published — showing both was confusing, so calendar cards hide this one.
+        if (showTimeAgo) TimeAgo(baseNote)
 
         MoreOptionsButton(
             baseNote = baseNote,

amethyst/src/main/res/values/strings.xml

@@ -583,6 +583,7 @@
     <string name="profile_badges_description">Choose which of the badges you\'ve received appear on your profile.</string>
     <string name="profile_badges_empty">You haven\'t received any badges yet.</string>
     <string name="pictures">Pictures</string>
+    <string name="calendars">Calendars</string>
     <string name="shorts">Shorts</string>
     <string name="public_chats">Public Chats</string>
     <string name="follow_packs">Follow Packs</string>
@@ -1851,6 +1852,8 @@
     <string name="route_global">Global</string>
     <string name="route_video">Shorts</string>
     <string name="route_pictures">Pictures</string>
+    <string name="route_calendars">Calendars</string>
+    <string name="route_calendar_collections">Calendar lists</string>
     <string name="route_chess">Chess</string>
     <string name="wallet">Wallet</string>
     <string name="wallet_balance">Balance</string>
@@ -1917,6 +1920,123 @@
     <string name="new_zap_poll">New Zap Poll</string>
     <string name="new_regular_poll">New Regular Poll</string>
     <string name="new_picture">New Picture</string>
+    <string name="new_calendar_event">New Calendar Event</string>
+    <string name="edit_calendar_event">Edit Calendar Event</string>
+    <string name="calendar_event_all_day_locked">Locked while editing — changing this would create a new event instead.</string>
+    <string name="new_calendar_collection">New Calendar</string>
+    <string name="edit_calendar_collection">Edit Calendar</string>
+    <string name="calendar_collection_events_section">Events in this calendar (%1$d)</string>
+    <string name="calendar_collection_no_events_yet">You haven\'t created any calendar events yet.</string>
+
+    <string name="calendar_view_feed">Feed</string>
+    <string name="calendar_view_month">Month</string>
+    <string name="calendar_view_week">Week</string>
+    <string name="calendar_view_day">Day</string>
+
+    <string name="calendar_section_upcoming">Upcoming</string>
+    <string name="calendar_section_past">Past</string>
+    <string name="calendar_empty_feed">No upcoming or past calendar events from your selected feed yet.</string>
+    <string name="calendar_empty_collections">No calendar collections yet.</string>
+    <string name="calendar_empty_feed_title">Your calendar is empty</string>
+    <string name="calendar_empty_feed_subtitle">Events shared by people you follow appear here. Tap the + button to create your own.</string>
+    <string name="calendar_empty_collections_title">No collections yet</string>
+    <string name="calendar_empty_collections_subtitle">Group events together — a meetup series, a conference track, your team\'s roadmap. Tap + to create one.</string>
+    <string name="calendar_empty_day_title">Nothing scheduled</string>
+    <string name="calendar_empty_day_subtitle">No events on this day. Tap + to add one.</string>
+    <string name="calendar_empty_week_title">Nothing this week</string>
+    <string name="calendar_empty_week_subtitle">No events fall in this week.</string>
+
+    <string name="calendar_event_title">Title</string>
+    <string name="calendar_event_summary">Summary</string>
+    <string name="calendar_event_location">Location</string>
+    <string name="calendar_event_image">Image URL</string>
+    <string name="calendar_event_all_day">All-day event</string>
+    <string name="calendar_event_start">Starts</string>
+    <string name="calendar_event_end">Ends</string>
+    <string name="calendar_event_hashtags">Hashtags (comma-separated)</string>
+    <string name="calendar_event_pick_date">Pick date</string>
+    <string name="calendar_event_pick_time">Pick time</string>
+    <string name="calendar_event_invalid">Title and start are required.</string>
+    <string name="calendar_event_end_before_start">End must be after start.</string>
+    <string name="calendar_nav_previous_month">Previous month</string>
+    <string name="calendar_nav_next_month">Next month</string>
+    <string name="calendar_nav_previous_week">Previous week</string>
+    <string name="calendar_nav_next_week">Next week</string>
+    <string name="calendar_nav_previous_day">Previous day</string>
+    <string name="calendar_nav_next_day">Next day</string>
+    <string name="calendar_no_events_today">No events on this day</string>
+    <string name="calendar_no_events">No events</string>
+    <string name="calendar_continues">Continues</string>
+    <string name="calendar_day_of_total">Day %1$d of %2$d</string>
+    <string name="calendar_add_to_phone_calendar">Add to phone calendar</string>
+    <string name="calendar_nav_jump_to_today">Jump to today</string>
+    <plurals name="calendar_day_a11y_events">
+        <item quantity="zero">%1$s, no events</item>
+        <item quantity="one">%1$s, %2$d event</item>
+        <item quantity="other">%1$s, %2$d events</item>
+    </plurals>
+    <string name="calendar_day_a11y_today_suffix">today</string>
+    <string name="calendar_day_a11y_selected_suffix">selected</string>
+    <string name="calendar_fab_new_event">Create a new calendar event</string>
+    <string name="calendar_fab_new_collection">Create a new calendar collection</string>
+    <string name="calendar_fab_toggle">Show create options</string>
+    <string name="calendar_untitled">(untitled)</string>
+    <string name="calendar_all_day">All-day</string>
+    <string name="calendar_rsvp_going_prefixed">✓ Going</string>
+    <string name="calendar_rsvp_maybe_prefixed">\? Maybe</string>
+    <string name="calendar_rsvp_not_going_prefixed">✗ Can\'t go</string>
+
+    <string name="calendar_collection_title">Title</string>
+    <string name="calendar_collection_description">Description</string>
+    <string name="calendar_collection_invalid">A title is required.</string>
+    <string name="calendar_collection_count">%1$d events</string>
+    <string name="calendar_collection_empty_members">No events in this calendar yet.</string>
+
+    <string name="calendar_rsvp_going">Going</string>
+    <string name="calendar_rsvp_maybe">Maybe</string>
+    <string name="calendar_rsvp_not_going">Can\'t go</string>
+    <string name="calendar_rsvp_section">RSVPs (%1$d)</string>
+    <string name="calendar_rsvp_none">No RSVPs yet.</string>
+    <string name="calendar_participants_section">Participants (%1$d)</string>
+    <string name="calendar_event_in_calendars">In calendars (%1$d)</string>
+    <string name="calendar_event_in_no_calendars">Not part of any calendar yet.</string>
+    <string name="calendar_event_loading">Loading event…</string>
+    <string name="calendar_relative_ongoing">Happening now</string>
+    <string name="calendar_relative_ongoing_with_end">%1$s · ends %2$s</string>
+    <string name="calendar_export_share_title">Share calendar event</string>
+    <string name="calendar_export_event">Export to calendar (.ics)</string>
+    <string name="calendar_reminder_channel_id">calendar_reminders</string>
+    <string name="calendar_reminder_channel_name">Calendar reminders</string>
+    <string name="calendar_reminder_channel_description">Heads-up when an event you\'re attending is about to start.</string>
+    <string name="calendar_reminder_default_title">Calendar event</string>
+    <string name="calendar_reminder_body">Starts in %1$d minutes</string>
+    <string name="calendar_add_to_calendar_action">Add to one of your calendars</string>
+    <string name="calendar_add_to_calendar_title">Add to a calendar</string>
+    <string name="calendar_add_to_calendar_none">You haven\'t created any calendars yet.</string>
+    <string name="calendar_collection_delete">Delete calendar</string>
+    <string name="calendar_collection_delete_confirm_title">Delete this calendar?</string>
+    <string name="calendar_collection_delete_confirm_message">The calendar list will be removed. Events inside it are not deleted.</string>
+    <string name="calendar_event_pick_image">Pick image</string>
+    <string name="calendar_event_image_upload_failed">Image upload failed</string>
+    <string name="calendar_event_image_upload_failed_body">The picked image couldn\'t be uploaded. Try again or paste a URL.</string>
+    <string name="calendar_event_participants_section">Participants (%1$d)</string>
+    <string name="calendar_event_participant_input">Search name, npub, or nip-05</string>
+    <string name="calendar_event_participant_invalid">Enter a valid npub… or 64-character hex pubkey.</string>
+    <string name="calendar_event_participant_remove">Remove participant</string>
+    <string name="calendar_reminder_settings_title">Calendar reminders</string>
+    <string name="calendar_reminder_settings_enabled_title">Send reminders</string>
+    <string name="calendar_reminder_settings_enabled_subtitle">A notification fires when an event you\'re attending is about to start.</string>
+    <string name="calendar_reminder_settings_lead_title">Reminder lead time</string>
+    <string name="calendar_reminder_settings_lead_subtitle">How many minutes before the event you want to be notified.</string>
+    <string name="calendar_reminder_settings_lead_choice">%1$d min</string>
+    <string name="calendar_share_nostr">Share as nostr link</string>
+    <string name="calendar_share_nostr_title">Share calendar link</string>
+    <string name="calendar_filter_all">All calendars</string>
+    <string name="calendar_filter_sheet_title">Show events from…</string>
+    <string name="calendar_filter_no_calendars">You haven\'t created any calendars yet.</string>
+    <string name="calendar_open_in_maps">Open in maps</string>
+    <string name="calendar_open_link">Open link</string>
+    <string name="route_calendar_event_detail">Event details</string>
     <string name="new_short_video">New Short Video</string>
     <string name="new_long_video">New Long Video</string>
 

amethyst/src/test/java/com/vitorpamplona/amethyst/calendar/CalendarEditLoadTest.kt

@@ -0,0 +1,129 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.calendar
+
+import com.vitorpamplona.quartz.nip01Core.tags.hashtags.hashtags
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+/**
+ * Smoke tests for the parsing path used by [NewCalendarEventViewModel.loadForEdit]. The VM
+ * itself can't be instantiated in a JVM test without the Account graph, but the per-field
+ * extraction logic delegates to Quartz accessors that are pure functions on the parsed event —
+ * exercising those here proves the round-trip from on-the-wire tags back to populated form
+ * fields.
+ */
+class CalendarEditLoadTest {
+    @Test
+    fun timeSlot_roundTripsAllFields() {
+        val event =
+            CalendarTimeSlotEvent(
+                id = "id",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags =
+                    arrayOf(
+                        arrayOf("d", "d-tag"),
+                        arrayOf("title", "Bitcoin meetup"),
+                        arrayOf("start", "1775671200"),
+                        arrayOf("end", "1775674800"),
+                        arrayOf("start_tzid", "Europe/Oslo"),
+                        arrayOf("summary", "An evening of stacking"),
+                        arrayOf("image", "https://example.com/img.png"),
+                        arrayOf("location", "Storgata 8"),
+                        arrayOf("t", "bitcoin"),
+                        arrayOf("t", "meetup"),
+                    ),
+                content = "Body",
+                sig = "sig",
+            )
+
+        assertEquals("Bitcoin meetup", event.title())
+        assertEquals(1775671200L, event.start())
+        assertEquals(1775674800L, event.end())
+        assertEquals("Europe/Oslo", event.startTzId())
+        assertEquals("An evening of stacking", event.summary())
+        assertEquals("https://example.com/img.png", event.image())
+        assertEquals("Storgata 8", event.location())
+        assertEquals(listOf("bitcoin", "meetup"), event.hashtags())
+    }
+
+    @Test
+    fun dateSlot_roundTripsAllFields() {
+        val event =
+            CalendarDateSlotEvent(
+                id = "id",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags =
+                    arrayOf(
+                        arrayOf("d", "d-tag"),
+                        arrayOf("title", "Conference"),
+                        arrayOf("start", "2025-01-15"),
+                        arrayOf("end", "2025-01-17"),
+                        arrayOf("summary", "Three day affair"),
+                        arrayOf("image", "https://example.com/banner.png"),
+                        arrayOf("location", "Lisbon"),
+                        arrayOf("t", "tech"),
+                    ),
+                content = "Body",
+                sig = "sig",
+            )
+
+        assertEquals("Conference", event.title())
+        assertEquals("2025-01-15", event.start())
+        assertEquals("2025-01-17", event.end())
+        assertEquals("Three day affair", event.summary())
+        assertEquals("https://example.com/banner.png", event.image())
+        assertEquals("Lisbon", event.location())
+        assertEquals(listOf("tech"), event.hashtags())
+    }
+
+    @Test
+    fun emptyFields_returnSafeDefaults() {
+        // An event with no optional tags should parse without exceptions; the VM substitutes
+        // empty-string defaults in those cases.
+        val event =
+            CalendarTimeSlotEvent(
+                id = "id",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags =
+                    arrayOf(
+                        arrayOf("d", "d-tag"),
+                        arrayOf("title", "Bare"),
+                        arrayOf("start", "1000000"),
+                    ),
+                content = "",
+                sig = "sig",
+            )
+
+        assertEquals("Bare", event.title())
+        assertEquals(1000000L, event.start())
+        assertEquals(null, event.end())
+        assertEquals(null, event.summary())
+        assertEquals(null, event.image())
+        assertEquals(null, event.location())
+        assertEquals(emptyList<String>(), event.hashtags())
+    }
+}

amethyst/src/test/java/com/vitorpamplona/amethyst/calendar/CalendarFeedGroupingTest.kt

@@ -0,0 +1,221 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.calendar
+
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.calendarLocalDayKeyRange
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.groupByDayKey
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.groupByDayKeyExpanded
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.partitionUpcomingPast
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import java.time.LocalDate
+import java.time.ZoneId
+
+class CalendarFeedGroupingTest {
+    @Test
+    fun groupByDayKey_dateSlotsLandOnIsoDate_inEveryZone() {
+        // The "Jan 15" appointment should bucket under Jan 15 regardless of viewer timezone —
+        // that's the contract for 31922 date-slot events. Previous UTC anchoring put it under
+        // Jan 14 for users in Pacific time.
+        val note = dateSlotNote(id = "d", start = "2025-01-15")
+        val grouped = groupByDayKey(listOf(note))
+        val expectedKey = LocalDate.of(2025, 1, 15).toEpochDay()
+        assertEquals(1, grouped[expectedKey]?.size)
+    }
+
+    @Test
+    fun groupByDayKey_timeSlotsBucketByLocalDate() {
+        // Same instant should yield the same local-date key regardless of how many calls we
+        // make — sanity check that the helper doesn't accidentally read the clock.
+        val note = timeSlotNote(id = "t", startSeconds = 1736942400L) // 2025-01-15 12:00 UTC
+        val grouped1 = groupByDayKey(listOf(note))
+        val grouped2 = groupByDayKey(listOf(note))
+        assertEquals(grouped1, grouped2)
+        assertEquals(1, grouped1.values.first().size)
+    }
+
+    @Test
+    fun groupByDayKey_multipleEventsSameDay_collectIntoOneBucket() {
+        val a = timeSlotNote(id = "a", startSeconds = 1736942400L) // 12:00 UTC
+        val b = timeSlotNote(id = "b", startSeconds = 1736942400L + 3600L) // 13:00 UTC
+        val c = timeSlotNote(id = "c", startSeconds = 1736942400L + 7200L) // 14:00 UTC
+        val grouped = groupByDayKey(listOf(a, b, c))
+        assertEquals(1, grouped.size)
+        assertEquals(3, grouped.values.first().size)
+    }
+
+    @Test
+    fun groupByDayKey_dropsNotesWithoutResolvedStart() {
+        val withoutStart = Note("ghost") // no event at all
+        val withStart = timeSlotNote(id = "with", startSeconds = 1736942400L)
+        val grouped = groupByDayKey(listOf(withoutStart, withStart))
+        assertEquals(1, grouped.size)
+        assertEquals(
+            "with",
+            grouped.values
+                .first()
+                .single()
+                .idHex,
+        )
+    }
+
+    @Test
+    fun partitionUpcomingPast_basicSplit() {
+        val now = 1_000_000L
+        val past = timeSlotNote(id = "past", startSeconds = now - 3600)
+        val future = timeSlotNote(id = "future", startSeconds = now + 3600)
+        val split = partitionUpcomingPast(listOf(past, future), nowSeconds = now)
+        assertEquals(1, split.upcoming.size)
+        assertEquals("future", split.upcoming[0].idHex)
+        assertEquals(1, split.past.size)
+        assertEquals("past", split.past[0].idHex)
+    }
+
+    @Test
+    fun partitionUpcomingPast_ongoingMultiDay_classifiedAsUpcoming() {
+        // Regression test for the audit fix: a 3-day conference that started yesterday and ends
+        // tomorrow should appear in "Upcoming", not "Past". The fix uses `end ?: start` so this
+        // case requires no relative-time guess.
+        val now = 1_000_000L
+        val ongoing = timeSlotNote(id = "ongoing", startSeconds = now - 86400, endSeconds = now + 86400)
+        val split = partitionUpcomingPast(listOf(ongoing), nowSeconds = now)
+        assertEquals("ongoing should be upcoming, not past", 1, split.upcoming.size)
+        assertEquals(0, split.past.size)
+    }
+
+    @Test
+    fun partitionUpcomingPast_dropsEventsWithoutStart() {
+        val ghost = Note("ghost")
+        val split = partitionUpcomingPast(listOf(ghost), nowSeconds = 1_000_000L)
+        assertEquals(0, split.upcoming.size)
+        assertEquals(0, split.past.size)
+    }
+
+    @Test
+    fun groupByDayKey_dateSlot_ignoresViewerTimezone_byUsingIsoDirectly() {
+        // We can't change the JVM zone mid-test reliably, but we can prove the date-slot path
+        // doesn't touch ZoneId by parsing a value-with-no-instant equivalent. The key for
+        // 2025-01-15 is always LocalDate.of(2025,1,15).toEpochDay() — a constant.
+        val note = dateSlotNote(id = "d", start = "2025-01-15")
+        val grouped = groupByDayKey(listOf(note))
+        val key = LocalDate.of(2025, 1, 15).toEpochDay()
+        assertNotNull(grouped[key])
+        // A neighbouring day key should be empty.
+        assertNull(grouped[key + 1])
+        assertNull(grouped[key - 1])
+    }
+
+    @Test
+    fun groupByDayKey_localDateInfoConsistentWithSystemZone() {
+        // For time-slot events the bucket key is the LocalDate in the system zone.
+        // We assert that the same instant maps to the same LocalDate as Java's stdlib derives.
+        val seconds = 1736942400L
+        val expectedKey =
+            java.time.Instant
+                .ofEpochSecond(seconds)
+                .atZone(ZoneId.systemDefault())
+                .toLocalDate()
+                .toEpochDay()
+        val grouped = groupByDayKey(listOf(timeSlotNote("x", startSeconds = seconds)))
+        assertTrue(grouped.containsKey(expectedKey))
+    }
+
+    @Test
+    fun groupByDayKeyExpanded_singleDayEvent_landsOnlyOnStartDay() {
+        // Sanity: an event with no end (or end == start) doesn't multiply itself.
+        val note = dateSlotNote(id = "d", start = "2025-01-15")
+        val grouped = groupByDayKeyExpanded(listOf(note))
+        val key = LocalDate.of(2025, 1, 15).toEpochDay()
+        assertEquals(1, grouped.size)
+        assertEquals(1, grouped[key]?.size)
+    }
+
+    @Test
+    fun groupByDayKeyExpanded_multiDayDateSlot_landsOnEveryDay() {
+        // A 3-day date-slot event should appear in each of Jan 15, 16, 17.
+        val note = dateSlotNote(id = "d", start = "2025-01-15", end = "2025-01-17")
+        val grouped = groupByDayKeyExpanded(listOf(note))
+        val keys = listOf(15, 16, 17).map { LocalDate.of(2025, 1, it).toEpochDay() }
+        assertEquals(3, grouped.size)
+        for (k in keys) assertEquals(1, grouped[k]?.size)
+    }
+
+    @Test
+    fun groupByDayKeyExpanded_multiDayTimeSlot_landsOnEveryDayCovered() {
+        // Spans ~36 hours from 12:00 UTC Jan 15 to 00:00 UTC Jan 17. Whether that crosses 2 or 3
+        // local days depends on the runner zone; we just assert it covers more than one day.
+        val note = timeSlotNote(id = "t", startSeconds = 1736942400L, endSeconds = 1736942400L + 36 * 3600L)
+        val grouped = groupByDayKeyExpanded(listOf(note))
+        assertTrue("expected multi-day event to land on >1 day", grouped.size >= 2)
+    }
+
+    @Test
+    fun calendarLocalDayKeyRange_isCappedAt366Days() {
+        // Defence: a malformed event with end years in the future shouldn't expand to thousands
+        // of day-keys and blow up the month grid.
+        val absurdStart = 1736942400L
+        val absurdEnd = absurdStart + 365L * 86400L * 10 // 10 years
+        val note = timeSlotNote(id = "rogue", startSeconds = absurdStart, endSeconds = absurdEnd)
+        val range = note.calendarLocalDayKeyRange()
+        assertNotNull(range)
+        assertTrue((range!!.last - range.first) <= 366)
+    }
+
+    // ---- helpers ----
+
+    private fun timeSlotNote(
+        id: String,
+        startSeconds: Long,
+        endSeconds: Long? = null,
+    ): Note {
+        val tags =
+            buildList {
+                add(arrayOf("d", "$id-d"))
+                add(arrayOf("title", "T"))
+                add(arrayOf("start", startSeconds.toString()))
+                endSeconds?.let { add(arrayOf("end", it.toString())) }
+            }.toTypedArray()
+        val e = CalendarTimeSlotEvent(id, "pub", 0L, tags, "", "sig")
+        return Note(id).apply { event = e }
+    }
+
+    private fun dateSlotNote(
+        id: String,
+        start: String,
+        end: String? = null,
+    ): Note {
+        val tags =
+            buildList {
+                add(arrayOf("d", "$id-d"))
+                add(arrayOf("title", "D"))
+                add(arrayOf("start", start))
+                end?.let { add(arrayOf("end", it)) }
+            }.toTypedArray()
+        val e = CalendarDateSlotEvent(id, "pub", 0L, tags, "", "sig")
+        return Note(id).apply { event = e }
+    }
+}

amethyst/src/test/java/com/vitorpamplona/amethyst/calendar/CalendarReminderPrefsTest.kt

@@ -0,0 +1,237 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.calendar
+
+import android.content.Context
+import android.content.SharedPreferences
+import com.vitorpamplona.amethyst.service.calendar.CalendarReminderPrefs
+import com.vitorpamplona.amethyst.service.calendar.CalendarReminderStore
+import io.mockk.every
+import io.mockk.mockk
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+
+/**
+ * Unit tests for the device-level reminder preferences and the per-event "already notified"
+ * store. Backed by an in-memory fake [SharedPreferences] so the test runs on the JVM without
+ * needing Robolectric.
+ */
+class CalendarReminderPrefsTest {
+    private lateinit var fakePrefs: FakeSharedPreferences
+    private lateinit var ctx: Context
+
+    @Before
+    fun setUp() {
+        fakePrefs = FakeSharedPreferences()
+        ctx = mockk()
+        every { ctx.getSharedPreferences(any(), any()) } returns fakePrefs
+    }
+
+    @Test
+    fun prefs_defaultsMatchPublicConstants() {
+        val prefs = CalendarReminderPrefs(ctx)
+        // Defaults are the contract callers in AppModules rely on — flipping these without an
+        // explicit migration would silently re-enable reminders for users who had turned them
+        // off (or vice versa).
+        assertEquals(CalendarReminderPrefs.DEFAULT_ENABLED, prefs.isEnabled())
+        assertEquals(CalendarReminderPrefs.DEFAULT_LEAD_MINUTES, prefs.leadMinutes())
+    }
+
+    @Test
+    fun prefs_setEnabled_roundTrips() {
+        val prefs = CalendarReminderPrefs(ctx)
+        prefs.setEnabled(false)
+        assertFalse(prefs.isEnabled())
+        prefs.setEnabled(true)
+        assertTrue(prefs.isEnabled())
+    }
+
+    @Test
+    fun prefs_setLeadMinutes_roundTrips() {
+        val prefs = CalendarReminderPrefs(ctx)
+        prefs.setLeadMinutes(30)
+        assertEquals(30, prefs.leadMinutes())
+    }
+
+    @Test
+    fun store_wasNotified_isFalseByDefault() {
+        val store = CalendarReminderStore(ctx)
+        assertFalse(store.wasNotified("event-a", 1_000_000L))
+    }
+
+    @Test
+    fun store_markNotified_makesWasNotifiedTrueForSameStart() {
+        val store = CalendarReminderStore(ctx)
+        store.markNotified("event-a", 1_000_000L)
+        assertTrue(store.wasNotified("event-a", 1_000_000L))
+    }
+
+    @Test
+    fun store_wasNotified_isFalseWhenStartChanges() {
+        // Regression test for the "moved meeting" case: if the author updates the appointment
+        // with a new start, the store should not silently swallow the new reminder.
+        val store = CalendarReminderStore(ctx)
+        store.markNotified("event-a", 1_000_000L)
+        assertFalse(store.wasNotified("event-a", 2_000_000L))
+    }
+
+    @Test
+    fun store_forgetBefore_dropsOldEntries() {
+        val store = CalendarReminderStore(ctx)
+        store.markNotified("old", 1_000_000L)
+        store.markNotified("recent", 5_000_000L)
+        store.forgetBefore(3_000_000L)
+        assertFalse(store.wasNotified("old", 1_000_000L))
+        assertTrue(store.wasNotified("recent", 5_000_000L))
+    }
+}
+
+/**
+ * Bare-bones in-memory implementation of [SharedPreferences] sufficient for the prefs/store
+ * round-trip tests. apply() is synchronous here — fine because the production code never relies
+ * on apply()'s async semantics.
+ */
+private class FakeSharedPreferences : SharedPreferences {
+    private val data = mutableMapOf<String, Any?>()
+
+    override fun getAll(): MutableMap<String, *> = data
+
+    override fun getString(
+        key: String,
+        defValue: String?,
+    ): String? = data[key] as? String ?: defValue
+
+    override fun getStringSet(
+        key: String,
+        defValues: MutableSet<String>?,
+    ): MutableSet<String>? {
+        @Suppress("UNCHECKED_CAST")
+        return data[key] as? MutableSet<String> ?: defValues
+    }
+
+    override fun getInt(
+        key: String,
+        defValue: Int,
+    ): Int = (data[key] as? Int) ?: defValue
+
+    override fun getLong(
+        key: String,
+        defValue: Long,
+    ): Long = (data[key] as? Long) ?: defValue
+
+    override fun getFloat(
+        key: String,
+        defValue: Float,
+    ): Float = (data[key] as? Float) ?: defValue
+
+    override fun getBoolean(
+        key: String,
+        defValue: Boolean,
+    ): Boolean = (data[key] as? Boolean) ?: defValue
+
+    override fun contains(key: String): Boolean = data.containsKey(key)
+
+    override fun edit(): SharedPreferences.Editor = FakeEditor(data)
+
+    override fun registerOnSharedPreferenceChangeListener(listener: SharedPreferences.OnSharedPreferenceChangeListener?) = Unit
+
+    override fun unregisterOnSharedPreferenceChangeListener(listener: SharedPreferences.OnSharedPreferenceChangeListener?) = Unit
+}
+
+private class FakeEditor(
+    private val data: MutableMap<String, Any?>,
+) : SharedPreferences.Editor {
+    private val pending = mutableMapOf<String, Any?>()
+    private val removed = mutableSetOf<String>()
+    private var clearAll = false
+
+    override fun putString(
+        key: String,
+        value: String?,
+    ): SharedPreferences.Editor {
+        pending[key] = value
+        return this
+    }
+
+    override fun putStringSet(
+        key: String,
+        values: MutableSet<String>?,
+    ): SharedPreferences.Editor {
+        pending[key] = values
+        return this
+    }
+
+    override fun putInt(
+        key: String,
+        value: Int,
+    ): SharedPreferences.Editor {
+        pending[key] = value
+        return this
+    }
+
+    override fun putLong(
+        key: String,
+        value: Long,
+    ): SharedPreferences.Editor {
+        pending[key] = value
+        return this
+    }
+
+    override fun putFloat(
+        key: String,
+        value: Float,
+    ): SharedPreferences.Editor {
+        pending[key] = value
+        return this
+    }
+
+    override fun putBoolean(
+        key: String,
+        value: Boolean,
+    ): SharedPreferences.Editor {
+        pending[key] = value
+        return this
+    }
+
+    override fun remove(key: String): SharedPreferences.Editor {
+        removed.add(key)
+        return this
+    }
+
+    override fun clear(): SharedPreferences.Editor {
+        clearAll = true
+        return this
+    }
+
+    override fun commit(): Boolean {
+        apply()
+        return true
+    }
+
+    override fun apply() {
+        if (clearAll) data.clear()
+        removed.forEach { data.remove(it) }
+        data.putAll(pending)
+    }
+}

amethyst/src/test/java/com/vitorpamplona/amethyst/calendar/CalendarSortKeysTest.kt

@@ -0,0 +1,204 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.calendar
+
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.appointmentView
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.calendarEndSeconds
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.calendarLocalDayKey
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.calendarStartSeconds
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.parseIsoDateToUnixSeconds
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.upcomingFirstCalendarOrder
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import java.time.LocalDate
+import java.time.ZoneId
+
+class CalendarSortKeysTest {
+    // 2025-01-15 12:00:00 UTC
+    private val sampleEpochSeconds = 1736942400L
+    private val sampleEpochSecondsPlus2h = sampleEpochSeconds + 7200L
+
+    @Test
+    fun parseIsoDateToUnixSeconds_validDate_anchorsAtLocalMidnight() {
+        val parsed = parseIsoDateToUnixSeconds("2025-01-15")
+        assertEquals(
+            "Should equal local midnight of Jan 15",
+            LocalDate.of(2025, 1, 15).atStartOfDay(ZoneId.systemDefault()).toEpochSecond(),
+            parsed,
+        )
+    }
+
+    @Test
+    fun parseIsoDateToUnixSeconds_blankOrNull_returnsNull() {
+        assertNull(parseIsoDateToUnixSeconds(null))
+        assertNull(parseIsoDateToUnixSeconds(""))
+        assertNull(parseIsoDateToUnixSeconds("   "))
+    }
+
+    @Test
+    fun parseIsoDateToUnixSeconds_invalidFormat_returnsNull() {
+        assertNull(parseIsoDateToUnixSeconds("01/15/2025"))
+        assertNull(parseIsoDateToUnixSeconds("2025-13-01")) // month 13
+        assertNull(parseIsoDateToUnixSeconds("garbage"))
+    }
+
+    @Test
+    fun calendarStartSeconds_timeSlot_returnsEventStart() {
+        val note = noteWithTimeSlot(start = sampleEpochSeconds, end = sampleEpochSecondsPlus2h)
+        assertEquals(sampleEpochSeconds, note.calendarStartSeconds())
+        assertEquals(sampleEpochSecondsPlus2h, note.calendarEndSeconds())
+    }
+
+    @Test
+    fun calendarStartSeconds_dateSlot_anchorsLocalMidnight() {
+        val note = noteWithDateSlot(start = "2025-01-15", end = "2025-01-17")
+        val expected = LocalDate.of(2025, 1, 15).atStartOfDay(ZoneId.systemDefault()).toEpochSecond()
+        assertEquals(expected, note.calendarStartSeconds())
+    }
+
+    @Test
+    fun calendarLocalDayKey_timeSlot_usesLocalCalendarDate() {
+        val note = noteWithTimeSlot(start = sampleEpochSeconds)
+        val expected =
+            java.time.Instant
+                .ofEpochSecond(sampleEpochSeconds)
+                .atZone(ZoneId.systemDefault())
+                .toLocalDate()
+                .toEpochDay()
+        assertEquals(expected, note.calendarLocalDayKey())
+    }
+
+    @Test
+    fun calendarLocalDayKey_dateSlot_usesIsoDirectly() {
+        // Date-only events must land on the ISO date in every zone — no zone conversion.
+        val note = noteWithDateSlot(start = "2025-01-15")
+        assertEquals(LocalDate.of(2025, 1, 15).toEpochDay(), note.calendarLocalDayKey())
+    }
+
+    @Test
+    fun appointmentView_timeSlot_mapsAllFields() {
+        val note = noteWithTimeSlot(start = sampleEpochSeconds, end = sampleEpochSecondsPlus2h)
+        val view = note.appointmentView()
+        assertTrue(view != null)
+        assertEquals("Demo", view!!.title)
+        assertEquals(false, view.isAllDay)
+        assertEquals(sampleEpochSeconds, view.startSeconds)
+        assertEquals(sampleEpochSecondsPlus2h, view.endSeconds)
+    }
+
+    @Test
+    fun appointmentView_dateSlot_isAllDayTrue() {
+        val note = noteWithDateSlot(start = "2025-01-15", end = "2025-01-16")
+        val view = note.appointmentView()
+        assertTrue(view != null)
+        assertEquals(true, view!!.isAllDay)
+    }
+
+    @Test
+    fun appointmentView_nonCalendarNote_returnsNull() {
+        val note = Note("no-event")
+        assertNull(note.appointmentView())
+    }
+
+    @Test
+    fun upcomingFirstOrder_upcomingBeforePast() {
+        val now = sampleEpochSeconds
+        val past = noteWithTimeSlot(id = "p", start = now - 3600)
+        val future = noteWithTimeSlot(id = "f", start = now + 3600)
+        val sorted = listOf(past, future).sortedWith(upcomingFirstCalendarOrder(now))
+        assertEquals("f", sorted[0].idHex)
+        assertEquals("p", sorted[1].idHex)
+    }
+
+    @Test
+    fun upcomingFirstOrder_twoFutureEvents_nearestFirst() {
+        val now = sampleEpochSeconds
+        val nearFuture = noteWithTimeSlot(id = "near", start = now + 100)
+        val farFuture = noteWithTimeSlot(id = "far", start = now + 10_000)
+        val sorted = listOf(farFuture, nearFuture).sortedWith(upcomingFirstCalendarOrder(now))
+        assertEquals("near", sorted[0].idHex)
+        assertEquals("far", sorted[1].idHex)
+    }
+
+    @Test
+    fun upcomingFirstOrder_twoPastEvents_mostRecentFirst() {
+        val now = sampleEpochSeconds
+        val recentPast = noteWithTimeSlot(id = "recent", start = now - 100)
+        val ancientPast = noteWithTimeSlot(id = "ancient", start = now - 10_000)
+        val sorted = listOf(ancientPast, recentPast).sortedWith(upcomingFirstCalendarOrder(now))
+        assertEquals("recent", sorted[0].idHex)
+        assertEquals("ancient", sorted[1].idHex)
+    }
+
+    @Test
+    fun upcomingFirstOrder_isTransitive_acrossNowBoundary() {
+        // Guards the previous bug where `TimeUtils.now()` was sampled inside the comparator: if
+        // the clock moved while sorting, an event's "upcoming" classification could flip between
+        // pair comparisons and trigger an IllegalArgumentException from the JDK sort. Snapshotting
+        // `now` once eliminates that.
+        val now = sampleEpochSeconds
+        val notes =
+            (0..20).map { i ->
+                noteWithTimeSlot(id = "n$i", start = now + (i - 10) * 60L)
+            }
+        // Should not throw.
+        notes.sortedWith(upcomingFirstCalendarOrder(now))
+    }
+
+    // ---- helpers ----
+
+    private fun noteWithTimeSlot(
+        id: String = "test-time",
+        start: Long,
+        end: Long? = null,
+    ): Note {
+        val tags =
+            buildList {
+                add(arrayOf("d", "$id-d"))
+                add(arrayOf("title", "Demo"))
+                add(arrayOf("start", start.toString()))
+                end?.let { add(arrayOf("end", it.toString())) }
+            }.toTypedArray()
+        val event = CalendarTimeSlotEvent(id, "pub", 0L, tags, "content", "sig")
+        return Note(id).apply { this.event = event }
+    }
+
+    private fun noteWithDateSlot(
+        id: String = "test-date",
+        start: String,
+        end: String? = null,
+    ): Note {
+        val tags =
+            buildList {
+                add(arrayOf("d", "$id-d"))
+                add(arrayOf("title", "Demo"))
+                add(arrayOf("start", start))
+                end?.let { add(arrayOf("end", it)) }
+            }.toTypedArray()
+        val event = CalendarDateSlotEvent(id, "pub", 0L, tags, "content", "sig")
+        return Note(id).apply { this.event = event }
+    }
+}

amethyst/src/test/java/com/vitorpamplona/amethyst/calendar/MonthGridBarsTest.kt

@@ -0,0 +1,129 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.calendar
+
+import com.vitorpamplona.amethyst.commons.model.nip52Calendar.computeMonthGridBars
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import java.time.LocalDate
+
+class MonthGridBarsTest {
+    @Test
+    fun singleDayEvent_oneSegment_bothEndsRounded() {
+        val note = dateSlot("a", "2025-01-15")
+        val key = LocalDate.of(2025, 1, 15).toEpochDay()
+        val byDay = computeMonthGridBars(listOf(note))
+        val seg = byDay[key]?.single()
+        assertNotNull(seg)
+        assertTrue("single-day event should round both ends", seg!!.isLeftEnd && seg.isRightEnd)
+        assertEquals(0, seg.lane)
+    }
+
+    @Test
+    fun threeDayEvent_segmentPerDay_endsOnlyOnBoundaries() {
+        val note = dateSlot("a", "2025-01-15", end = "2025-01-17")
+        val byDay = computeMonthGridBars(listOf(note))
+        val k15 = LocalDate.of(2025, 1, 15).toEpochDay()
+        val k16 = LocalDate.of(2025, 1, 16).toEpochDay()
+        val k17 = LocalDate.of(2025, 1, 17).toEpochDay()
+        assertEquals(true to false, byDay[k15]!!.single().run { isLeftEnd to isRightEnd })
+        assertEquals(false to false, byDay[k16]!!.single().run { isLeftEnd to isRightEnd })
+        assertEquals(false to true, byDay[k17]!!.single().run { isLeftEnd to isRightEnd })
+    }
+
+    @Test
+    fun overlappingEvents_assignedToDistinctLanes() {
+        // A: Jan 15–17. B: Jan 16–18. They overlap on 16 and 17 so must land in different lanes.
+        val a = dateSlot("a", "2025-01-15", end = "2025-01-17")
+        val b = dateSlot("b", "2025-01-16", end = "2025-01-18")
+        val byDay = computeMonthGridBars(listOf(a, b))
+        val k16 = LocalDate.of(2025, 1, 16).toEpochDay()
+        val lanes = byDay[k16]!!.map { it.lane }.toSet()
+        assertEquals("expected two distinct lanes on the overlap day", 2, lanes.size)
+    }
+
+    @Test
+    fun longerEventTakesLowerLane_amongTies() {
+        // Earliest-start ties broken by length-descending: the longer event sits on lane 0 so it
+        // visually anchors the top, with the shorter one tucked under it.
+        val long3 = dateSlot("L", "2025-01-15", end = "2025-01-17")
+        val short1 = dateSlot("S", "2025-01-15")
+        val byDay = computeMonthGridBars(listOf(short1, long3))
+        val k15 = byDay[LocalDate.of(2025, 1, 15).toEpochDay()]!!
+        val longLane = k15.first { it.note === long3 }.lane
+        val shortLane = k15.first { it.note === short1 }.lane
+        assertTrue("longer event should be in a lower lane", longLane < shortLane)
+    }
+
+    @Test
+    fun nonOverlappingEvents_reuseLowestLane() {
+        // A: Jan 15. B: Jan 16. C: Jan 17. No overlaps → all on lane 0.
+        val a = dateSlot("a", "2025-01-15")
+        val b = dateSlot("b", "2025-01-16")
+        val c = dateSlot("c", "2025-01-17")
+        val byDay = computeMonthGridBars(listOf(a, b, c))
+        for (note in listOf(a, b, c)) {
+            val key =
+                note.event!!
+                    .tags
+                    .first { it[0] == "start" }[1]
+                    .let(LocalDate::parse)
+                    .toEpochDay()
+            assertEquals(0, byDay[key]!!.single().lane)
+        }
+    }
+
+    @Test
+    fun noEvents_emptyMap() {
+        val byDay = computeMonthGridBars(emptyList())
+        assertTrue(byDay.isEmpty())
+    }
+
+    @Test
+    fun noteWithoutStart_dropped() {
+        val ghost = Note("ghost") // no event
+        val real = dateSlot("a", "2025-01-15")
+        val byDay = computeMonthGridBars(listOf(ghost, real))
+        assertEquals(1, byDay.size)
+        assertNull(byDay[0L])
+    }
+
+    private fun dateSlot(
+        id: String,
+        start: String,
+        end: String? = null,
+    ): Note {
+        val tags =
+            buildList {
+                add(arrayOf("d", "$id-d"))
+                add(arrayOf("title", "T"))
+                add(arrayOf("start", start))
+                end?.let { add(arrayOf("end", it)) }
+            }.toTypedArray()
+        val e = CalendarDateSlotEvent(id, "pub", 0L, tags, "", "sig")
+        return Note(id).apply { event = e }
+    }
+}

amethyst/src/test/java/com/vitorpamplona/amethyst/calendar/RsvpDTagTest.kt

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.calendar
+
+import com.vitorpamplona.amethyst.ui.note.types.rsvpAddressFor
+import com.vitorpamplona.amethyst.ui.note.types.rsvpDTagFor
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip52Calendar.rsvp.CalendarRSVPEvent
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotEquals
+import org.junit.Test
+
+class RsvpDTagTest {
+    private val targetA = Address(31923, "alice-pubkey", "my-event")
+    private val targetB = Address(31922, "bob-pubkey", "another-event")
+    private val myPubKey = "me-pubkey"
+
+    @Test
+    fun rsvpDTag_isDeterministic_forSameTarget() {
+        // Two calls for the same target must produce the same d-tag — that's the dedupe
+        // contract that makes RSVP buttons reflect "my current status" rather than a history
+        // of taps.
+        assertEquals(rsvpDTagFor(targetA), rsvpDTagFor(targetA))
+    }
+
+    @Test
+    fun rsvpDTag_differsAcrossTargets() {
+        assertNotEquals(rsvpDTagFor(targetA), rsvpDTagFor(targetB))
+    }
+
+    @Test
+    fun rsvpDTag_encodesAllAddressComponents() {
+        // Make sure the d-tag is stable across kind + pubkey + dtag axes, so a copy-paste of
+        // the same dTag across different kinds (or different authors) doesn't collide.
+        val sameKind = Address(targetA.kind, "another-pub", targetA.dTag)
+        val sameAuthor = Address(targetA.kind, targetA.pubKeyHex, "another-dtag")
+        val sameDtagDifferentKind = Address(31922, targetA.pubKeyHex, targetA.dTag)
+
+        val original = rsvpDTagFor(targetA)
+        assertNotEquals(original, rsvpDTagFor(sameKind))
+        assertNotEquals(original, rsvpDTagFor(sameAuthor))
+        assertNotEquals(original, rsvpDTagFor(sameDtagDifferentKind))
+    }
+
+    @Test
+    fun rsvpAddressFor_usesRsvpKindAndMyPubKey() {
+        val addr = rsvpAddressFor(myPubKey, targetA)
+        assertEquals(CalendarRSVPEvent.KIND, addr.kind)
+        assertEquals(myPubKey, addr.pubKeyHex)
+        assertEquals(rsvpDTagFor(targetA), addr.dTag)
+    }
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/icons/symbols/MaterialSymbols.kt

@@ -97,6 +97,7 @@ object MaterialSymbols {
     val EmojiEmotions = MaterialSymbol("\uEA22")
     val Error = MaterialSymbol("\uF8B6")
     val ErrorOutline = MaterialSymbol("\uF8B6")
+    val EventAvailable = MaterialSymbol("\uE614")
     val ExpandLess = MaterialSymbol("\uE5CE")
     val ExpandMore = MaterialSymbol("\uE5CF")
     val Explore = MaterialSymbol("\uE87A")

commons/src/jvmAndroid/kotlin/com/vitorpamplona/amethyst/commons/model/nip52Calendar/CalendarAppointmentView.kt

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.model.nip52Calendar
+
+import androidx.compose.runtime.Immutable
+import com.vitorpamplona.amethyst.commons.model.Note
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+
+/**
+ * Shared projection of NIP-52 calendar appointments. The 31922 (date-slot) and 31923 (time-slot)
+ * event classes have identical UI surfaces but no common interface, so UI code repeated a
+ * `when (event) { is Time -> e.title(); is Date -> e.title() }` block per accessor. Materialising
+ * the projection once collapses those branches into a single linear read.
+ *
+ * [isAllDay] discriminates the two kinds; [startSeconds] is local-midnight for 31922 (matching
+ * the rest of the calendar code's day-anchoring).
+ */
+@Immutable
+data class CalendarAppointmentView(
+    val title: String?,
+    val image: String?,
+    val summary: String?,
+    val location: String?,
+    val startSeconds: Long?,
+    val endSeconds: Long?,
+    val isAllDay: Boolean,
+)
+
+fun Note.appointmentView(): CalendarAppointmentView? =
+    when (val e = event) {
+        is CalendarTimeSlotEvent ->
+            CalendarAppointmentView(
+                title = e.title(),
+                image = e.image(),
+                summary = e.summary(),
+                location = e.location(),
+                startSeconds = e.start(),
+                endSeconds = e.end() ?: e.start(),
+                isAllDay = false,
+            )
+        is CalendarDateSlotEvent ->
+            CalendarAppointmentView(
+                title = e.title(),
+                image = e.image(),
+                summary = e.summary(),
+                location = e.location(),
+                startSeconds = parseIsoDateToUnixSeconds(e.start()),
+                endSeconds = parseIsoDateToUnixSeconds(e.end()) ?: parseIsoDateToUnixSeconds(e.start()),
+                isAllDay = true,
+            )
+        else -> null
+    }

commons/src/jvmAndroid/kotlin/com/vitorpamplona/amethyst/commons/model/nip52Calendar/CalendarSortKeys.kt

@@ -0,0 +1,185 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.model.nip52Calendar
+
+import com.vitorpamplona.amethyst.commons.model.Note
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import com.vitorpamplona.quartz.utils.TimeUtils
+import java.time.Instant
+import java.time.LocalDate
+import java.time.ZoneId
+import java.time.format.DateTimeFormatter
+
+// java.time formatters are thread-safe; the SimpleDateFormat predecessor was shared by sort
+// (background) and grouping (UI) paths and could throw under concurrent use.
+private val IsoDateParser: DateTimeFormatter = DateTimeFormatter.ISO_LOCAL_DATE
+
+private fun parseIsoDate(date: String?): LocalDate? {
+    if (date.isNullOrBlank()) return null
+    return try {
+        LocalDate.parse(date, IsoDateParser)
+    } catch (_: Throwable) {
+        null
+    }
+}
+
+/**
+ * Calendar 31922 carries a calendar date (no instant). Anchor it at local midnight so that
+ * "Jan 15" lands on Jan 15 in the user's grid and ordering reflects their local zone — UTC
+ * anchoring made date-only events appear a day early west of UTC.
+ */
+fun parseIsoDateToUnixSeconds(date: String?): Long? = parseIsoDate(date)?.atStartOfDay(ZoneId.systemDefault())?.toEpochSecond()
+
+/**
+ * Unified start time as unix-seconds. For 31923 (time-slot) this is the event's instant; for
+ * 31922 (date-slot) it is local midnight of the calendar date. Both are suitable for ordering
+ * against [TimeUtils.now] and for relative-time rendering.
+ */
+fun Note.calendarStartSeconds(): Long? =
+    when (val e = event) {
+        is CalendarTimeSlotEvent -> e.start()
+        is CalendarDateSlotEvent -> parseIsoDateToUnixSeconds(e.start())
+        else -> null
+    }
+
+fun Note.calendarEndSeconds(): Long? =
+    when (val e = event) {
+        is CalendarTimeSlotEvent -> e.end() ?: e.start()
+        is CalendarDateSlotEvent -> parseIsoDateToUnixSeconds(e.end()) ?: parseIsoDateToUnixSeconds(e.start())
+        else -> null
+    }
+
+/**
+ * Calendar-day bucket key (days since 1970-01-01) for grouping events into day cells.
+ *
+ * For 31923, the event's instant is converted to the viewer's local date; for 31922, the ISO
+ * date string is parsed directly with no zone conversion (a calendar date for "Jan 15" must
+ * land on Jan 15 in every zone). Returns null when the start cannot be resolved.
+ */
+fun Note.calendarLocalDayKey(): Long? =
+    when (val e = event) {
+        is CalendarTimeSlotEvent ->
+            e.start()?.let {
+                Instant
+                    .ofEpochSecond(it)
+                    .atZone(ZoneId.systemDefault())
+                    .toLocalDate()
+                    .toEpochDay()
+            }
+        is CalendarDateSlotEvent -> parseIsoDate(e.start())?.toEpochDay()
+        else -> null
+    }
+
+/**
+ * Buckets appointments by local calendar day (returned as `LocalDate.toEpochDay`). Notes that
+ * are not calendar appointments or whose start can't be parsed are dropped.
+ */
+fun groupByDayKey(notes: List<Note>): Map<Long, List<Note>> {
+    val map = mutableMapOf<Long, MutableList<Note>>()
+    notes.forEach {
+        val dayKey = it.calendarLocalDayKey() ?: return@forEach
+        map.getOrPut(dayKey) { mutableListOf() }.add(it)
+    }
+    return map
+}
+
+/**
+ * Inclusive `[start, end]` range of day-keys an appointment covers. A single-day event yields
+ * one key; a multi-day event yields every day from start through end. Returns null when the
+ * note isn't a calendar appointment or has no parseable start.
+ *
+ * Capped at 366 days so a malformed event with a far-future end can't blow up month-view memory.
+ */
+fun Note.calendarLocalDayKeyRange(): LongRange? {
+    val startKey = calendarLocalDayKey() ?: return null
+    val endKey =
+        when (val e = event) {
+            is CalendarTimeSlotEvent ->
+                e.end()?.let {
+                    Instant
+                        .ofEpochSecond(it)
+                        .atZone(ZoneId.systemDefault())
+                        .toLocalDate()
+                        .toEpochDay()
+                } ?: startKey
+            is CalendarDateSlotEvent -> parseIsoDate(e.end())?.toEpochDay() ?: startKey
+            else -> startKey
+        }
+    val safeEnd = endKey.coerceAtLeast(startKey).coerceAtMost(startKey + 366)
+    return startKey..safeEnd
+}
+
+/**
+ * Like [groupByDayKey] but a multi-day appointment lands in every day it covers (not just the
+ * start day). Used by month/week/day views so a 3-day conference shows on all three rows; the
+ * upcoming/past list view still uses [groupByDayKey] semantics via its own ordering.
+ */
+fun groupByDayKeyExpanded(notes: List<Note>): Map<Long, List<Note>> {
+    val map = mutableMapOf<Long, MutableList<Note>>()
+    notes.forEach { note ->
+        val range = note.calendarLocalDayKeyRange() ?: return@forEach
+        for (key in range) {
+            map.getOrPut(key) { mutableListOf() }.add(note)
+        }
+    }
+    return map
+}
+
+/**
+ * Sort by: upcoming events ascending (closest first), then past events descending (most-recent
+ * first). [nowSeconds] is captured once per sort so the comparator stays transitive across the
+ * full sort run — reading the clock inside `compare` would violate the [Comparator] contract on
+ * boundary elements.
+ */
+fun upcomingFirstCalendarOrder(nowSeconds: Long): Comparator<Note> =
+    Comparator { a, b ->
+        val sa = a.calendarStartSeconds()
+        val sb = b.calendarStartSeconds()
+
+        val primary =
+            when {
+                sa == null && sb == null -> compareCreatedAt(a, b)
+                sa == null -> 1
+                sb == null -> -1
+                else -> {
+                    val aUpcoming = sa >= nowSeconds
+                    val bUpcoming = sb >= nowSeconds
+                    when {
+                        aUpcoming && !bUpcoming -> -1
+                        !aUpcoming && bUpcoming -> 1
+                        aUpcoming -> sa.compareTo(sb) // both future: nearest first
+                        else -> sb.compareTo(sa) // both past: most recent first
+                    }
+                }
+            }
+
+        if (primary != 0) primary else a.idHex.compareTo(b.idHex)
+    }
+
+private fun compareCreatedAt(
+    a: Note,
+    b: Note,
+): Int {
+    val ca = a.createdAt() ?: 0L
+    val cb = b.createdAt() ?: 0L
+    return cb.compareTo(ca)
+}

commons/src/jvmAndroid/kotlin/com/vitorpamplona/amethyst/commons/model/nip52Calendar/IcsExport.kt

@@ -0,0 +1,212 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.model.nip52Calendar
+
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+import java.time.Instant
+import java.time.LocalDate
+import java.time.ZoneOffset
+import java.time.format.DateTimeFormatter
+
+/**
+ * Serialises NIP-52 calendar events to RFC 5545 iCalendar (`.ics`) text. The output is the
+ * universal calendar interchange format: tapping a generated file in any email/calendar app
+ * lets users import the event into Google Calendar, Apple Calendar, Outlook, Thunderbird, etc.
+ *
+ * Implements only the subset needed for NIP-52 appointments:
+ *  - `VEVENT` per appointment with `UID`, `DTSTAMP`, `DTSTART`, `DTEND`, `SUMMARY`,
+ *    `DESCRIPTION`, `LOCATION`, and `CATEGORIES` for hashtags.
+ *  - 31922 date-slot events emit `DTSTART;VALUE=DATE:YYYYMMDD` (no time component); 31923
+ *    time-slot events emit UTC instants formatted as `YYYYMMDDTHHMMSSZ`.
+ *  - 31924 calendar collections wrap their member appointments in one `VCALENDAR`.
+ *
+ * Line folding (75-octet limit per RFC 5545) is *not* implemented — modern parsers tolerate
+ * long lines and the resulting files import cleanly across the apps tested.
+ */
+object IcsExport {
+    private const val PRODID = "-//Amethyst//NIP-52//EN"
+    private const val CRLF = "\r\n"
+    private val UtcStamp: DateTimeFormatter = DateTimeFormatter.ofPattern("yyyyMMdd'T'HHmmss'Z'")
+    private val IsoBasicDate: DateTimeFormatter = DateTimeFormatter.ofPattern("yyyyMMdd")
+
+    fun appointmentToIcs(
+        event: Any,
+        address: Address,
+        nowSeconds: Long,
+    ): String {
+        val sb = StringBuilder()
+        sb.append("BEGIN:VCALENDAR").append(CRLF)
+        sb.append("VERSION:2.0").append(CRLF)
+        sb.append("PRODID:").append(PRODID).append(CRLF)
+        sb.append("CALSCALE:GREGORIAN").append(CRLF)
+        appendVEvent(sb, event, address, nowSeconds)
+        sb.append("END:VCALENDAR").append(CRLF)
+        return sb.toString()
+    }
+
+    /**
+     * Wrap multiple appointments (the membership of a kind-31924 calendar) in one VCALENDAR.
+     * Members that aren't in [memberEvents] are silently skipped — typically because they
+     * haven't been fetched from relays yet.
+     */
+    fun calendarToIcs(
+        calendar: CalendarEvent,
+        memberEvents: List<Pair<Address, Any>>,
+        nowSeconds: Long,
+    ): String {
+        val sb = StringBuilder()
+        sb.append("BEGIN:VCALENDAR").append(CRLF)
+        sb.append("VERSION:2.0").append(CRLF)
+        sb.append("PRODID:").append(PRODID).append(CRLF)
+        sb.append("CALSCALE:GREGORIAN").append(CRLF)
+        calendar.title()?.let {
+            sb.append("X-WR-CALNAME:").append(escapeText(it)).append(CRLF)
+        }
+        calendar.content.takeIf { it.isNotBlank() }?.let {
+            sb.append("X-WR-CALDESC:").append(escapeText(it)).append(CRLF)
+        }
+        memberEvents.forEach { (address, event) ->
+            appendVEvent(sb, event, address, nowSeconds)
+        }
+        sb.append("END:VCALENDAR").append(CRLF)
+        return sb.toString()
+    }
+
+    /**
+     * Suggested filename for a single appointment. Sanitises the title for filesystems but
+     * keeps it short enough for share-sheet thumbnails. Falls back to the d-tag.
+     */
+    fun appointmentFilename(
+        event: Any,
+        address: Address,
+    ): String {
+        val title =
+            when (event) {
+                is CalendarTimeSlotEvent -> event.title()
+                is CalendarDateSlotEvent -> event.title()
+                else -> null
+            }
+        return safeFilename(title ?: address.dTag) + ".ics"
+    }
+
+    fun calendarFilename(calendar: CalendarEvent): String = safeFilename(calendar.title() ?: "calendar") + ".ics"
+
+    private fun safeFilename(raw: String): String =
+        raw
+            .replace(Regex("[^a-zA-Z0-9._-]+"), "-")
+            .trim('-', '_')
+            .ifBlank { "calendar" }
+            .take(60)
+
+    private fun appendVEvent(
+        sb: StringBuilder,
+        event: Any,
+        address: Address,
+        nowSeconds: Long,
+    ) {
+        sb.append("BEGIN:VEVENT").append(CRLF)
+        // UID must be globally unique; "<dtag>@<pubkey>.nostr" gives stable uniqueness without
+        // exposing relay metadata.
+        sb
+            .append("UID:")
+            .append(address.dTag)
+            .append('@')
+            .append(address.pubKeyHex)
+            .append(".nostr")
+            .append(CRLF)
+        sb.append("DTSTAMP:").append(formatUtcInstant(nowSeconds)).append(CRLF)
+
+        when (event) {
+            is CalendarTimeSlotEvent -> appendTimeSlot(sb, event)
+            is CalendarDateSlotEvent -> appendDateSlot(sb, event)
+        }
+
+        sb.append("END:VEVENT").append(CRLF)
+    }
+
+    private fun appendTimeSlot(
+        sb: StringBuilder,
+        event: CalendarTimeSlotEvent,
+    ) {
+        event.start()?.let { sb.append("DTSTART:").append(formatUtcInstant(it)).append(CRLF) }
+        event.end()?.let { sb.append("DTEND:").append(formatUtcInstant(it)).append(CRLF) }
+        event.title()?.let { sb.append("SUMMARY:").append(escapeText(it)).append(CRLF) }
+        appendDescription(sb, event.summary().orEmpty().ifBlank { event.content })
+        event.location()?.let { sb.append("LOCATION:").append(escapeText(it)).append(CRLF) }
+        appendCategories(sb, event.hashtags())
+    }
+
+    private fun appendDateSlot(
+        sb: StringBuilder,
+        event: CalendarDateSlotEvent,
+    ) {
+        event.start()?.let { iso ->
+            tryFormatBasicDate(iso)?.let { sb.append("DTSTART;VALUE=DATE:").append(it).append(CRLF) }
+        }
+        event.end()?.let { iso ->
+            tryFormatBasicDate(iso)?.let { sb.append("DTEND;VALUE=DATE:").append(it).append(CRLF) }
+        }
+        event.title()?.let { sb.append("SUMMARY:").append(escapeText(it)).append(CRLF) }
+        appendDescription(sb, event.summary().orEmpty().ifBlank { event.content })
+        event.location()?.let { sb.append("LOCATION:").append(escapeText(it)).append(CRLF) }
+        appendCategories(sb, event.hashtags())
+    }
+
+    private fun appendDescription(
+        sb: StringBuilder,
+        text: String,
+    ) {
+        if (text.isBlank()) return
+        sb.append("DESCRIPTION:").append(escapeText(text)).append(CRLF)
+    }
+
+    private fun appendCategories(
+        sb: StringBuilder,
+        hashtags: List<String>,
+    ) {
+        if (hashtags.isEmpty()) return
+        sb.append("CATEGORIES:").append(hashtags.joinToString(",") { escapeText(it) }).append(CRLF)
+    }
+
+    private fun formatUtcInstant(unixSeconds: Long): String = UtcStamp.format(Instant.ofEpochSecond(unixSeconds).atOffset(ZoneOffset.UTC))
+
+    private fun tryFormatBasicDate(iso: String): String? =
+        try {
+            IsoBasicDate.format(LocalDate.parse(iso))
+        } catch (_: Throwable) {
+            null
+        }
+
+    /**
+     * Escapes text per RFC 5545 §3.3.11: backslash, semicolon, comma, newline. Carriage
+     * returns are dropped (line folding handles physical newlines for us).
+     */
+    internal fun escapeText(raw: String): String =
+        raw
+            .replace("\\", "\\\\")
+            .replace("\n", "\\n")
+            .replace("\r", "")
+            .replace(",", "\\,")
+            .replace(";", "\\;")
+}

commons/src/jvmAndroid/kotlin/com/vitorpamplona/amethyst/commons/model/nip52Calendar/MonthGridBars.kt

@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.model.nip52Calendar
+
+import androidx.compose.runtime.Immutable
+import com.vitorpamplona.amethyst.commons.model.Note
+
+/**
+ * One bar drawn into one day cell, with `lane` controlling its vertical position so two
+ * overlapping multi-day events stack rather than collide. `isLeftEnd` / `isRightEnd` control
+ * which corners of the bar are rounded — a continuation day in the middle of a 3-day event gets
+ * neither end rounded, so adjacent cells visually merge into one bar.
+ *
+ * Note: the underlying [Note] is exposed so the UI can colour or label bars per event. Equality
+ * is on idHex so a row of cells holding the same bar share segment identity for keys.
+ */
+@Immutable
+data class MonthGridBarSegment(
+    val note: Note,
+    val lane: Int,
+    val isLeftEnd: Boolean,
+    val isRightEnd: Boolean,
+)
+
+/**
+ * Maximum lanes we render before collapsing the remainder into a "+N" overflow label. Three
+ * matches the previous dot-row capacity and keeps each 56dp cell readable on mid-range phones.
+ */
+const val MONTH_GRID_MAX_LANES = 3
+
+/**
+ * Greedy lane-assignment for the month grid: sort events earliest-start-first (longer events
+ * wins ties so they take the top lane), then for each event pick the lowest lane index whose
+ * full day-range is unoccupied. Returns a per-day-key map so each cell can render its own
+ * segments without re-running the layout.
+ *
+ * Single-day events participate in the same layout — they get bars too, just short ones,
+ * which keeps the visual language consistent.
+ */
+fun computeMonthGridBars(notes: List<Note>): Map<Long, List<MonthGridBarSegment>> {
+    val ranges =
+        notes
+            .distinctBy { it.idHex }
+            .mapNotNull { n -> n.calendarLocalDayKeyRange()?.let { n to it } }
+            .sortedWith(
+                compareBy(
+                    { it.second.first },
+                    { -(it.second.last - it.second.first) },
+                    { it.first.idHex },
+                ),
+            )
+
+    // day-key → set of lanes already claimed for that day
+    val occupied = mutableMapOf<Long, MutableSet<Int>>()
+    val perDay = mutableMapOf<Long, MutableList<MonthGridBarSegment>>()
+
+    for ((note, range) in ranges) {
+        // Find the lowest lane index whose full range is free. Bounded at 32 so a pathological
+        // input can't loop forever; overflow events still render as "+N" via the cap downstream.
+        var lane = 0
+        while (lane < 32) {
+            val clash = (range).any { occupied[it]?.contains(lane) == true }
+            if (!clash) break
+            lane++
+        }
+        for (day in range) {
+            occupied.getOrPut(day) { mutableSetOf() }.add(lane)
+            perDay.getOrPut(day) { mutableListOf() }.add(
+                MonthGridBarSegment(
+                    note = note,
+                    lane = lane,
+                    isLeftEnd = day == range.first,
+                    isRightEnd = day == range.last,
+                ),
+            )
+        }
+    }
+    // Within each cell, sort by lane so the rendering doesn't have to.
+    return perDay.mapValues { (_, list) -> list.sortedBy { it.lane } }
+}

commons/src/jvmTest/kotlin/com/vitorpamplona/amethyst/commons/model/nip52Calendar/IcsExportTest.kt

@@ -0,0 +1,252 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.model.nip52Calendar
+
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.calendar.CalendarEvent
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class IcsExportTest {
+    private val nowSeconds = 1_700_000_000L // 2023-11-14 22:13:20 UTC
+
+    @Test
+    fun timeSlot_producesWellFormedVCalendar() {
+        // 1700000000 = 2023-11-14 22:13:20 UTC; +1h = 2023-11-14 23:13:20 UTC.
+        val event =
+            CalendarTimeSlotEvent(
+                id = "id",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags =
+                    arrayOf(
+                        arrayOf("d", "my-event"),
+                        arrayOf("title", "Bitcoin meetup"),
+                        arrayOf("start", "1700000000"),
+                        arrayOf("end", "1700003600"),
+                        arrayOf("location", "Storgata 8"),
+                    ),
+                content = "Casual hang",
+                sig = "sig",
+            )
+        val ics = IcsExport.appointmentToIcs(event, Address(31923, "pub", "my-event"), nowSeconds)
+
+        // Outer envelope is required by every RFC 5545 parser.
+        assertTrue("must wrap in VCALENDAR", ics.contains("BEGIN:VCALENDAR\r\n"))
+        assertTrue("must close VCALENDAR", ics.endsWith("END:VCALENDAR\r\n"))
+        assertTrue("must include VEVENT", ics.contains("BEGIN:VEVENT\r\n"))
+        assertTrue("must close VEVENT", ics.contains("END:VEVENT\r\n"))
+        assertTrue("must have version", ics.contains("VERSION:2.0"))
+
+        // Time-slot stamps are UTC instants.
+        assertTrue("DTSTART must be UTC instant", ics.contains("DTSTART:20231114T221320Z"))
+        assertTrue("DTEND must be UTC instant", ics.contains("DTEND:20231114T231320Z"))
+
+        assertTrue("summary present", ics.contains("SUMMARY:Bitcoin meetup"))
+        assertTrue("location present", ics.contains("LOCATION:Storgata 8"))
+        assertTrue("description present", ics.contains("DESCRIPTION:Casual hang"))
+        assertTrue("UID format", ics.contains("UID:my-event@pub.nostr"))
+    }
+
+    @Test
+    fun dateSlot_emitsDateValueWithoutTimeComponent() {
+        val event =
+            CalendarDateSlotEvent(
+                id = "id",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags =
+                    arrayOf(
+                        arrayOf("d", "conf"),
+                        arrayOf("title", "Conference"),
+                        arrayOf("start", "2025-01-15"),
+                        arrayOf("end", "2025-01-17"),
+                    ),
+                content = "",
+                sig = "sig",
+            )
+        val ics = IcsExport.appointmentToIcs(event, Address(31922, "pub", "conf"), nowSeconds)
+
+        // Date-only events use VALUE=DATE so calendar apps don't render them as midnight events.
+        assertTrue("date-slot DTSTART carries VALUE=DATE", ics.contains("DTSTART;VALUE=DATE:20250115"))
+        assertTrue("date-slot DTEND carries VALUE=DATE", ics.contains("DTEND;VALUE=DATE:20250117"))
+        assertFalse("date-slot must not include time component", ics.contains("DTSTART:20250115T"))
+    }
+
+    @Test
+    fun escapeText_quotesSpecialCharacters() {
+        // RFC 5545 §3.3.11: backslash, comma, semicolon, newline are reserved.
+        assertEquals("a\\\\b", IcsExport.escapeText("a\\b"))
+        assertEquals("a\\,b", IcsExport.escapeText("a,b"))
+        assertEquals("a\\;b", IcsExport.escapeText("a;b"))
+        assertEquals("line1\\nline2", IcsExport.escapeText("line1\nline2"))
+        assertEquals("a", IcsExport.escapeText("a\r"))
+    }
+
+    @Test
+    fun escapingFiresInSummaryAndDescription() {
+        val event =
+            CalendarTimeSlotEvent(
+                id = "id",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags =
+                    arrayOf(
+                        arrayOf("d", "x"),
+                        arrayOf("title", "Hi, world; happy"),
+                        arrayOf("start", "1700000000"),
+                    ),
+                content = "line1\nline2",
+                sig = "sig",
+            )
+        val ics = IcsExport.appointmentToIcs(event, Address(31923, "pub", "x"), nowSeconds)
+        // The escaped string must keep the surrounding `SUMMARY:` prefix and survive whatever
+        // line folding parsers re-apply.
+        assertTrue("comma escaped", ics.contains("SUMMARY:Hi\\, world\\; happy"))
+        assertTrue("newline escaped", ics.contains("DESCRIPTION:line1\\nline2"))
+    }
+
+    @Test
+    fun hashtags_renderAsCategoriesLine() {
+        val event =
+            CalendarTimeSlotEvent(
+                id = "id",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags =
+                    arrayOf(
+                        arrayOf("d", "x"),
+                        arrayOf("title", "T"),
+                        arrayOf("start", "1700000000"),
+                        arrayOf("t", "bitcoin"),
+                        arrayOf("t", "meetup"),
+                    ),
+                content = "",
+                sig = "sig",
+            )
+        val ics = IcsExport.appointmentToIcs(event, Address(31923, "pub", "x"), nowSeconds)
+        assertTrue("CATEGORIES line present", ics.contains("CATEGORIES:bitcoin,meetup"))
+    }
+
+    @Test
+    fun calendarToIcs_wrapsAllMembers() {
+        val a =
+            CalendarTimeSlotEvent(
+                id = "a",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags =
+                    arrayOf(
+                        arrayOf("d", "a"),
+                        arrayOf("title", "A"),
+                        arrayOf("start", "1700000000"),
+                    ),
+                content = "",
+                sig = "sig",
+            )
+        val b =
+            CalendarDateSlotEvent(
+                id = "b",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags =
+                    arrayOf(
+                        arrayOf("d", "b"),
+                        arrayOf("title", "B"),
+                        arrayOf("start", "2025-02-01"),
+                    ),
+                content = "",
+                sig = "sig",
+            )
+        val calendar =
+            CalendarEvent(
+                id = "cal",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags = arrayOf(arrayOf("d", "my-cal"), arrayOf("title", "My Calendar")),
+                content = "All my events",
+                sig = "sig",
+            )
+        val ics =
+            IcsExport.calendarToIcs(
+                calendar,
+                listOf(
+                    Address(31923, "pub", "a") to a,
+                    Address(31922, "pub", "b") to b,
+                ),
+                nowSeconds,
+            )
+
+        assertTrue("calendar name present", ics.contains("X-WR-CALNAME:My Calendar"))
+        assertTrue("calendar description present", ics.contains("X-WR-CALDESC:All my events"))
+        // Both members must appear inside the one VCALENDAR.
+        assertEquals(
+            "exactly two VEVENT blocks",
+            2,
+            "BEGIN:VEVENT".toRegex().findAll(ics).count(),
+        )
+        assertTrue("member A present", ics.contains("UID:a@pub.nostr"))
+        assertTrue("member B present", ics.contains("UID:b@pub.nostr"))
+    }
+
+    @Test
+    fun filename_sanitisesPathSeparatorsAndSpaces() {
+        val event =
+            CalendarTimeSlotEvent(
+                id = "id",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags =
+                    arrayOf(
+                        arrayOf("d", "x"),
+                        arrayOf("title", "Slashes / & spaces .,;"),
+                        arrayOf("start", "1700000000"),
+                    ),
+                content = "",
+                sig = "sig",
+            )
+        val name = IcsExport.appointmentFilename(event, Address(31923, "pub", "x"))
+        // Must end with .ics and contain no filesystem-hostile characters.
+        assertTrue(name.endsWith(".ics"))
+        assertFalse("no slashes", name.contains('/'))
+        assertFalse("no commas", name.contains(','))
+        assertFalse("no semicolons", name.contains(';'))
+    }
+
+    @Test
+    fun filename_fallsBackToDTagWhenTitleAbsent() {
+        val event =
+            CalendarTimeSlotEvent(
+                id = "id",
+                pubKey = "pub",
+                createdAt = 0L,
+                tags = arrayOf(arrayOf("d", "fallback-dtag"), arrayOf("start", "1700000000")),
+                content = "",
+                sig = "sig",
+            )
+        val name = IcsExport.appointmentFilename(event, Address(31923, "pub", "fallback-dtag"))
+        assertEquals("fallback-dtag.ics", name)
+    }
+}