docs(design): mark contact special-dates implemented + note deviations

Records the UID_2445 (vs SYNC_DATA1) identity decision, the sync-time age
snapshot, and the seeded reminder default; checks off the #14/#15 task lists.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -8,6 +8,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
+- See your contacts' birthdays and anniversaries in your calendar. A new,
+  **optional** feature (Settings → Contact special dates) mirrors your contacts'
+  birthdays, anniversaries and other dates into local "Birthdays",
+  "Anniversaries" and "Other dates" calendars that stay in sync as your contacts
+  change. Each is a normal local calendar, so you set its colour, visibility and
+  reminders the usual way — new birthdays even start with a reminder a week before
+  *and* on the day. The title format is yours to customise (`{name}`, `{age}`).
+  This is the first feature to use the contacts permission: it is requested only
+  when you turn the feature on, everything stays on your device (Calendula has no
+  internet access), and your contacts are only ever read, never changed. Thanks
+  to @moonj for the suggestion ([#15]).
 - Set more than one default reminder per calendar. A calendar's default
   reminders — and the global defaults under Settings → Notifications — can now
   hold several lead times instead of just one, so new events can start with, say,
@@ -752,5 +763,6 @@ automatically, with zero telemetry and no internet permission.
 [#12]: https://codeberg.org/jlmakiola/calendula/issues/12
 [#13]: https://codeberg.org/jlmakiola/calendula/issues/13
 [#14]: https://codeberg.org/jlmakiola/calendula/issues/14
+[#15]: https://codeberg.org/jlmakiola/calendula/issues/15
 [#16]: https://codeberg.org/jlmakiola/calendula/issues/16
 [#17]: https://codeberg.org/jlmakiola/calendula/issues/17

app/src/main/AndroidManifest.xml

@@ -5,6 +5,15 @@
     <uses-permission android:name="android.permission.READ_CALENDAR" />
     <uses-permission android:name="android.permission.WRITE_CALENDAR" />
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+    <!--
+      Optional and feature-gated: only the "Contact special dates" feature reads
+      contacts, and only after the user enables it and grants this at runtime
+      (never requested at startup). Everything stays offline — birthdays and
+      other contact dates are mirrored one-way into local calendars; contacts
+      are never written and nothing leaves the device (the app has no INTERNET
+      permission). See docs/design/contact-special-dates.md.
+    -->
+    <uses-permission android:name="android.permission.READ_CONTACTS" />
     <!--
       Lets the "Reliable delivery" setting open the direct system dialog to
       exempt Calendula from battery optimisation (so reminder broadcasts aren't

app/src/main/java/de/jeanlucmakiola/calendula/CalendulaApp.kt

@@ -5,6 +5,8 @@ import dagger.hilt.android.EntryPointAccessors
 import dagger.hilt.android.HiltAndroidApp
 import de.jeanlucmakiola.calendula.data.backup.BackupScheduler
 import de.jeanlucmakiola.calendula.data.backup.BackupWorker
+import de.jeanlucmakiola.calendula.data.contacts.SpecialDatesScheduler
+import de.jeanlucmakiola.calendula.data.contacts.SpecialDatesSyncWorker
 import de.jeanlucmakiola.calendula.data.crash.CrashReporter
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -25,6 +27,7 @@ class CalendulaApp : Application() {
         // respecting, on-device; the user submits the report by hand).
         CrashReporter.install(this)
         reconcileAutoBackup()
+        reconcileSpecialDates()
     }
 
     /**
@@ -44,4 +47,21 @@ class CalendulaApp : Application() {
             )
         }
     }
+
+    /**
+     * Re-arm (or cancel) the daily special-dates reconcile from the saved
+     * settings on every launch — like [reconcileAutoBackup], this cancels
+     * orphaned work after the feature is turned off and re-schedules after a
+     * reinstall. The foreground trigger (RootScreen ON_RESUME) does the on-open
+     * refresh, so no immediate run is needed here.
+     */
+    private fun reconcileSpecialDates() {
+        val deps = EntryPointAccessors.fromApplication(this, SpecialDatesSyncWorker.Deps::class.java)
+        CoroutineScope(SupervisorJob() + Dispatchers.Default).launch {
+            SpecialDatesScheduler.apply(
+                context = this@CalendulaApp,
+                enabled = deps.settingsPrefs().specialDatesEnabled.first(),
+            )
+        }
+    }
 }

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarDataSource.kt

@@ -24,6 +24,7 @@ import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
 import de.jeanlucmakiola.calendula.domain.EventStatus
 import de.jeanlucmakiola.calendula.domain.Reminder
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
 import de.jeanlucmakiola.calendula.domain.ics.IcsEvent
 import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
 import de.jeanlucmakiola.calendula.domain.rruleTruncatedAt
@@ -97,6 +98,41 @@ interface CalendarDataSource {
     /** Permanently delete a local calendar the app owns, with all its events. */
     fun deleteCalendar(id: Long)
 
+    /**
+     * Create a local calendar tagged as the special-dates mirror for [type]
+     * (a marker in `CAL_SYNC2`); returns its `Calendars._ID`. Otherwise a normal
+     * local calendar, so it inherits per-calendar colour/visibility/reminders.
+     */
+    fun createManagedCalendar(displayName: String, color: Int, type: SpecialDateType): Long
+
+    /**
+     * The app's special-dates calendars, found by their `CAL_SYNC2` marker.
+     * Lets the mirror re-adopt its calendars after the stored ids are lost, and
+     * detect when the user deleted one in system settings.
+     */
+    fun findManagedCalendars(): List<ManagedCalendarRow>
+
+    /**
+     * The managed events in [calendarId] (those carrying a `UID_2445`, not
+     * soft-deleted) as [ManagedEventRow]s — the existing side of the sync diff.
+     */
+    fun queryManagedEvents(calendarId: Long): List<ManagedEventRow>
+
+    /**
+     * Insert a managed event carrying the deterministic [uid] in `UID_2445`;
+     * seeds its reminder rows from [form] (never touched again by sync). Returns
+     * the new `Events._ID`. [allDayReminderTimeMinutes]: see [insertEvent].
+     */
+    fun insertManagedEvent(form: EventForm, uid: String, allDayReminderTimeMinutes: Int): Long
+
+    /**
+     * Overwrite exactly the given managed columns on [eventId] (keys are
+     * `CalendarContract.Events` columns; a null value clears the column). A
+     * bare, targeted update — it never reconciles reminders or attendees, so
+     * user-owned data on the event survives every sync. No-ops on an empty map.
+     */
+    fun updateManagedFields(eventId: Long, values: Map<String, Any?>)
+
     /**
      * Insert a new event; returns the new `Events._ID`. [allDayReminderTimeMinutes]
      * (minutes from local midnight) is the wall-clock time all-day reminders
@@ -292,6 +328,134 @@ class AndroidCalendarDataSource @Inject constructor(
         if (deleted == 0) throw WriteFailedException("delete calendar id=$id")
     }
 
+    override fun createManagedCalendar(displayName: String, color: Int, type: SpecialDateType): Long {
+        val name = displayName.trim().ifEmpty { Fallbacks.UNNAMED_CALENDAR }
+        val values = ContentValues().apply {
+            put(CalendarContract.Calendars.ACCOUNT_NAME, LOCAL_ACCOUNT_NAME)
+            put(CalendarContract.Calendars.ACCOUNT_TYPE, CalendarContract.ACCOUNT_TYPE_LOCAL)
+            put(CalendarContract.Calendars.OWNER_ACCOUNT, LOCAL_ACCOUNT_NAME)
+            put(CalendarContract.Calendars.NAME, name)
+            put(CalendarContract.Calendars.CALENDAR_DISPLAY_NAME, name)
+            put(CalendarContract.Calendars.CALENDAR_COLOR, color)
+            put(
+                CalendarContract.Calendars.CALENDAR_ACCESS_LEVEL,
+                CalendarContract.Calendars.CAL_ACCESS_OWNER,
+            )
+            put(CalendarContract.Calendars.VISIBLE, 1)
+            put(CalendarContract.Calendars.SYNC_EVENTS, 1)
+            // The marker that identifies this as our special-dates calendar,
+            // independent of the (user-editable) display name. CAL_SYNC1 already
+            // holds the description, so the marker lives in CAL_SYNC2.
+            put(MANAGED_MARKER_COLUMN, markerFor(type))
+        }
+        val uri = resolver.insert(localCalendarsUri(), values)
+            ?: throw WriteFailedException("create managed calendar")
+        return ContentUris.parseId(uri)
+    }
+
+    override fun findManagedCalendars(): List<ManagedCalendarRow> = resolver.query(
+        CalendarContract.Calendars.CONTENT_URI,
+        arrayOf(CalendarContract.Calendars._ID, MANAGED_MARKER_COLUMN),
+        "${CalendarContract.Calendars.ACCOUNT_TYPE} = ? AND " +
+            "${CalendarContract.Calendars.ACCOUNT_NAME} = ? AND " +
+            "$MANAGED_MARKER_COLUMN IS NOT NULL",
+        arrayOf(CalendarContract.ACCOUNT_TYPE_LOCAL, LOCAL_ACCOUNT_NAME),
+        null,
+    )?.use { c ->
+        buildList {
+            while (c.moveToNext()) {
+                val type = typeForMarker(c.getString(1)) ?: continue
+                add(ManagedCalendarRow(id = c.getLong(0), type = type))
+            }
+        }
+    } ?: emptyList()
+
+    override fun queryManagedEvents(calendarId: Long): List<ManagedEventRow> = resolver.query(
+        CalendarContract.Events.CONTENT_URI,
+        arrayOf(
+            CalendarContract.Events._ID,
+            CalendarContract.Events.UID_2445,
+            CalendarContract.Events.TITLE,
+            CalendarContract.Events.DTSTART,
+            CalendarContract.Events.RRULE,
+        ),
+        "${CalendarContract.Events.CALENDAR_ID} = ? AND " +
+            "${CalendarContract.Events.DELETED} = 0 AND " +
+            "${CalendarContract.Events.UID_2445} IS NOT NULL",
+        arrayOf(calendarId.toString()),
+        null,
+    )?.use { c ->
+        buildList {
+            while (c.moveToNext()) {
+                val uid = c.getString(1)?.takeIf { it.isNotEmpty() } ?: continue
+                add(
+                    ManagedEventRow(
+                        eventId = c.getLong(0),
+                        uid = uid,
+                        title = c.getString(2).orEmpty(),
+                        dtStartMillis = c.getLong(3),
+                        rrule = c.getString(4)?.takeIf { it.isNotEmpty() },
+                    ),
+                )
+            }
+        }
+    } ?: emptyList()
+
+    override fun insertManagedEvent(form: EventForm, uid: String, allDayReminderTimeMinutes: Int): Long {
+        val times = form.toWriteTimes(ZoneId.systemDefault())
+        val values = ContentValues().apply {
+            put(
+                CalendarContract.Events.CALENDAR_ID,
+                requireNotNull(form.calendarId) { "EventForm.calendarId is required" },
+            )
+            // Deterministic UID = the reconciliation key. A re-sync reads it back
+            // (queryManagedEvents) and diffs on it, so a contact never doubles.
+            put(CalendarContract.Events.UID_2445, uid)
+            put(CalendarContract.Events.TITLE, form.title.trim())
+            put(CalendarContract.Events.ALL_DAY, if (form.isAllDay) 1 else 0)
+            put(CalendarContract.Events.DTSTART, times.dtStartMillis)
+            if (form.rrule == null) {
+                put(CalendarContract.Events.DTEND, times.dtEndMillis)
+            } else {
+                put(CalendarContract.Events.RRULE, form.rrule)
+                put(CalendarContract.Events.DURATION, times.toRfc2445Duration(form.isAllDay))
+            }
+            put(CalendarContract.Events.EVENT_TIMEZONE, times.timezone)
+            put(CalendarContract.Events.AVAILABILITY, form.availability.toProviderValue())
+            put(CalendarContract.Events.ACCESS_LEVEL, form.accessLevel.toProviderValue())
+            form.location.trim().takeIf { it.isNotEmpty() }
+                ?.let { put(CalendarContract.Events.EVENT_LOCATION, it) }
+            form.description.trim().takeIf { it.isNotEmpty() }
+                ?.let { put(CalendarContract.Events.DESCRIPTION, it) }
+        }
+        val eventId = resolver.insert(CalendarContract.Events.CONTENT_URI, values)
+            ?.let(ContentUris::parseId)
+            ?: throw WriteFailedException("insert managed event into calendar id=${form.calendarId}")
+        // Seeded once, then never re-touched by sync — so a user who moves a
+        // birthday reminder keeps their change.
+        encodedReminders(form, allDayReminderTimeMinutes).forEach { minutes ->
+            val reminder = ContentValues().apply {
+                put(CalendarContract.Reminders.EVENT_ID, eventId)
+                put(CalendarContract.Reminders.MINUTES, minutes)
+                put(CalendarContract.Reminders.METHOD, CalendarContract.Reminders.METHOD_ALERT)
+            }
+            if (resolver.insert(CalendarContract.Reminders.CONTENT_URI, reminder) == null) {
+                Log.w(TAG, "Failed to attach reminder ($minutes min) to managed event $eventId")
+            }
+        }
+        return eventId
+    }
+
+    override fun updateManagedFields(eventId: Long, values: Map<String, Any?>) {
+        if (values.isEmpty()) return
+        val rows = resolver.update(
+            ContentUris.withAppendedId(CalendarContract.Events.CONTENT_URI, eventId),
+            values.toContentValues(),
+            null, null,
+        )
+        if (rows == 0) throw WriteFailedException("update managed event id=$eventId")
+    }
+
     override fun instances(beginMillis: Long, endMillis: Long): List<EventInstance> {
         ensureObserversRegistered()
         val uri = CalendarContract.Instances.CONTENT_URI.buildUpon().apply {
@@ -1038,6 +1202,17 @@ class AndroidCalendarDataSource @Inject constructor(
         while (moveToNext()) mapper(this@mapAllNotNull)?.let(::add)
     }
 
+    /** The `CAL_SYNC2` marker value identifying a managed calendar's [type]. */
+    private fun markerFor(type: SpecialDateType): String = when (type) {
+        SpecialDateType.Birthday -> "$MANAGED_MARKER_PREFIX:birthday"
+        SpecialDateType.Anniversary -> "$MANAGED_MARKER_PREFIX:anniversary"
+        SpecialDateType.Custom -> "$MANAGED_MARKER_PREFIX:custom"
+    }
+
+    /** Inverse of [markerFor]; null for a value that isn't one of ours. */
+    private fun typeForMarker(marker: String?): SpecialDateType? =
+        SpecialDateType.entries.firstOrNull { markerFor(it) == marker }
+
     private companion object {
         const val TAG = "CalendarDataSource"
 
@@ -1047,6 +1222,13 @@ class AndroidCalendarDataSource @Inject constructor(
          */
         const val LOCAL_ACCOUNT_NAME = "Calendula"
 
+        /**
+         * Column and namespace for the special-dates marker. CAL_SYNC1 already
+         * holds the local-calendar description, so the marker uses CAL_SYNC2.
+         */
+        val MANAGED_MARKER_COLUMN: String = CalendarContract.Calendars.CAL_SYNC2
+        const val MANAGED_MARKER_PREFIX = "calendula.specialdates"
+
         /**
          * How far ahead/behind a search looks for a recurring event's nearest
          * occurrence (~2 years). Wide enough for everyday series; a series that

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/ManagedCalendar.kt

@@ -0,0 +1,24 @@
+package de.jeanlucmakiola.calendula.data.calendar
+
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
+
+/**
+ * One of the app's special-dates calendars, discovered by the marker stamped in
+ * its `CAL_SYNC2` column — so the mirror can re-adopt its calendars even if the
+ * stored ids in preferences were lost (e.g. an app-data wipe).
+ */
+data class ManagedCalendarRow(val id: Long, val type: SpecialDateType)
+
+/**
+ * A managed event as read back for the sync diff. [uid] is the deterministic
+ * `Events.UID_2445` (`contact-<type>:<lookupKey>@calendula`) the mirror keys on;
+ * [title], [dtStartMillis] and [rrule] are the managed columns compared against
+ * the desired state to decide whether a targeted update is needed.
+ */
+data class ManagedEventRow(
+    val eventId: Long,
+    val uid: String,
+    val title: String,
+    val dtStartMillis: Long,
+    val rrule: String?,
+)

app/src/main/java/de/jeanlucmakiola/calendula/data/contacts/AndroidSpecialDatesCalendarSpec.kt

@@ -0,0 +1,41 @@
+package de.jeanlucmakiola.calendula.data.contacts
+
+import android.content.Context
+import dagger.hilt.android.qualifiers.ApplicationContext
+import de.jeanlucmakiola.calendula.R
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Resolves the localized calendar names/templates and per-type colours the
+ * mirror creates its calendars with. The colours are picked from the shared
+ * palette so managed calendars look native alongside user calendars.
+ */
+@Singleton
+class AndroidSpecialDatesCalendarSpec @Inject constructor(
+    @ApplicationContext private val context: Context,
+) : SpecialDatesCalendarSpec {
+
+    override fun displayName(type: SpecialDateType): String = context.getString(
+        when (type) {
+            SpecialDateType.Birthday -> R.string.special_dates_calendar_birthday
+            SpecialDateType.Anniversary -> R.string.special_dates_calendar_anniversary
+            SpecialDateType.Custom -> R.string.special_dates_calendar_custom
+        },
+    )
+
+    override fun defaultTitleTemplate(type: SpecialDateType): String = context.getString(
+        when (type) {
+            SpecialDateType.Birthday -> R.string.special_dates_default_title_birthday
+            SpecialDateType.Anniversary -> R.string.special_dates_default_title_anniversary
+            SpecialDateType.Custom -> R.string.special_dates_default_title_custom
+        },
+    )
+
+    override fun color(type: SpecialDateType): Int = when (type) {
+        SpecialDateType.Birthday -> 0xFF8E24AA.toInt() // purple
+        SpecialDateType.Anniversary -> 0xFFD50000.toInt() // red
+        SpecialDateType.Custom -> 0xFF039BE5.toInt() // blue
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/contacts/ContactSpecialDatesDataSource.kt

@@ -0,0 +1,98 @@
+package de.jeanlucmakiola.calendula.data.contacts
+
+import android.Manifest
+import android.content.Context
+import android.content.pm.PackageManager
+import android.provider.ContactsContract
+import android.provider.ContactsContract.CommonDataKinds.Event
+import android.util.Log
+import androidx.core.content.ContextCompat
+import dagger.hilt.android.qualifiers.ApplicationContext
+import de.jeanlucmakiola.calendula.domain.contacts.ContactSpecialDate
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
+import de.jeanlucmakiola.calendula.domain.contacts.parseContactEventDate
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Reads the dated `Event` rows (birthdays, anniversaries, custom dates) of the
+ * device's contacts. Read-only and offline — the one-way source for the
+ * special-dates mirror. Requires `READ_CONTACTS`; returns an empty list when
+ * the permission is absent so the sync can degrade to a stalled state rather
+ * than crash.
+ */
+interface ContactSpecialDatesDataSource {
+    fun hasPermission(): Boolean
+
+    /** All usable contact special-dates, deduplicated per contact and type. */
+    fun readSpecialDates(): List<ContactSpecialDate>
+}
+
+/** Map a `ContactsContract` event `TYPE` to our calendar bucket. */
+internal fun specialDateTypeForRawEventType(type: Int): SpecialDateType = when (type) {
+    Event.TYPE_BIRTHDAY -> SpecialDateType.Birthday
+    Event.TYPE_ANNIVERSARY -> SpecialDateType.Anniversary
+    else -> SpecialDateType.Custom
+}
+
+@Singleton
+class AndroidContactSpecialDatesDataSource @Inject constructor(
+    @ApplicationContext private val context: Context,
+) : ContactSpecialDatesDataSource {
+
+    override fun hasPermission(): Boolean =
+        ContextCompat.checkSelfPermission(context, Manifest.permission.READ_CONTACTS) ==
+            PackageManager.PERMISSION_GRANTED
+
+    override fun readSpecialDates(): List<ContactSpecialDate> {
+        if (!hasPermission()) return emptyList()
+        val resolver = context.contentResolver
+        // A contact can carry the same date more than once (multiple raw
+        // contacts under one aggregate); keep the first per (contact, type).
+        val seen = HashSet<Pair<String, SpecialDateType>>()
+        val result = ArrayList<ContactSpecialDate>()
+        runCatching {
+            resolver.query(
+                ContactsContract.Data.CONTENT_URI,
+                PROJECTION,
+                "${ContactsContract.Data.MIMETYPE} = ?",
+                arrayOf(Event.CONTENT_ITEM_TYPE),
+                null,
+            )?.use { c ->
+                val idxDate = c.getColumnIndexOrThrow(Event.START_DATE)
+                val idxType = c.getColumnIndexOrThrow(Event.TYPE)
+                val idxLabel = c.getColumnIndexOrThrow(Event.LABEL)
+                val idxLookup = c.getColumnIndexOrThrow(ContactsContract.Data.LOOKUP_KEY)
+                val idxName = c.getColumnIndexOrThrow(ContactsContract.Data.DISPLAY_NAME_PRIMARY)
+                while (c.moveToNext()) {
+                    val lookup = c.getString(idxLookup)?.takeIf { it.isNotEmpty() } ?: continue
+                    val parts = parseContactEventDate(c.getString(idxDate)) ?: continue
+                    val type = specialDateTypeForRawEventType(c.getInt(idxType))
+                    if (!seen.add(lookup to type)) continue
+                    result += ContactSpecialDate(
+                        lookupKey = lookup,
+                        displayName = c.getString(idxName)?.trim().orEmpty(),
+                        type = type,
+                        month = parts.month,
+                        day = parts.day,
+                        year = parts.year,
+                        label = c.getString(idxLabel)?.takeIf { it.isNotBlank() },
+                    )
+                }
+            }
+        }.onFailure { Log.w(TAG, "Reading contact special-dates failed", it) }
+        return result
+    }
+
+    private companion object {
+        const val TAG = "ContactSpecialDates"
+
+        val PROJECTION = arrayOf(
+            ContactsContract.Data.LOOKUP_KEY,
+            ContactsContract.Data.DISPLAY_NAME_PRIMARY,
+            Event.START_DATE,
+            Event.TYPE,
+            Event.LABEL,
+        )
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/contacts/SpecialDatesScheduler.kt

@@ -0,0 +1,123 @@
+package de.jeanlucmakiola.calendula.data.contacts
+
+import android.content.Context
+import android.util.Log
+import androidx.work.CoroutineWorker
+import androidx.work.Data
+import androidx.work.ExistingPeriodicWorkPolicy
+import androidx.work.ExistingWorkPolicy
+import androidx.work.OneTimeWorkRequestBuilder
+import androidx.work.PeriodicWorkRequestBuilder
+import androidx.work.WorkManager
+import androidx.work.WorkerParameters
+import dagger.hilt.EntryPoint
+import dagger.hilt.InstallIn
+import dagger.hilt.android.EntryPointAccessors
+import dagger.hilt.components.SingletonComponent
+import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
+import de.jeanlucmakiola.calendula.data.prefs.SpecialDatesStalledReason
+import kotlinx.coroutines.flow.first
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.todayIn
+import java.util.concurrent.TimeUnit
+import kotlin.time.Clock
+
+/**
+ * Schedules the contact special-dates mirror. Birthdays change rarely, so this
+ * is deliberately cheap: a **daily** periodic reconcile, plus an immediate run
+ * on enable / "Sync now" and a debounced one when the app is foregrounded. No
+ * ContentObserver — it would need the process alive and buys almost nothing for
+ * once-a-year events. Everything stays offline (local contacts → local calendar).
+ */
+object SpecialDatesScheduler {
+
+    private const val WORK_NAME = "special-dates-sync"
+    private const val WORK_NAME_NOW = "special-dates-sync-now"
+    private const val KEY_FOREGROUND = "foreground"
+
+    /** Enqueue (or cancel) the daily periodic reconcile to match [enabled]. */
+    fun apply(context: Context, enabled: Boolean) {
+        val workManager = WorkManager.getInstance(context)
+        if (!enabled) {
+            workManager.cancelUniqueWork(WORK_NAME)
+            workManager.cancelUniqueWork(WORK_NAME_NOW)
+            return
+        }
+        val request = PeriodicWorkRequestBuilder<SpecialDatesSyncWorker>(1, TimeUnit.DAYS)
+            // Delay the first periodic run so it never overlaps an immediate run.
+            .setInitialDelay(1, TimeUnit.DAYS)
+            .build()
+        workManager.enqueueUniquePeriodicWork(WORK_NAME, ExistingPeriodicWorkPolicy.UPDATE, request)
+    }
+
+    /**
+     * Run one reconcile immediately. [foreground] runs are debounced (the app can
+     * resume often); enable/"Sync now" runs ([foreground] false) always sync.
+     */
+    fun runNow(context: Context, foreground: Boolean = false) {
+        val request = OneTimeWorkRequestBuilder<SpecialDatesSyncWorker>()
+            .setInputData(Data.Builder().putBoolean(KEY_FOREGROUND, foreground).build())
+            .build()
+        WorkManager.getInstance(context)
+            .enqueueUniqueWork(WORK_NAME_NOW, ExistingWorkPolicy.REPLACE, request)
+    }
+
+    internal const val INPUT_FOREGROUND = KEY_FOREGROUND
+}
+
+/**
+ * Runs the [SpecialDatesSyncEngine]. Pulls its collaborators through a Hilt
+ * [EntryPoint] so it works under WorkManager's default worker factory. Records
+ * the run for the settings status line; a missing permission parks the feature
+ * in a stalled state (surfaced in settings) rather than retrying forever.
+ */
+class SpecialDatesSyncWorker(
+    appContext: Context,
+    params: WorkerParameters,
+) : CoroutineWorker(appContext, params) {
+
+    @EntryPoint
+    @InstallIn(SingletonComponent::class)
+    interface Deps {
+        fun settingsPrefs(): SettingsPrefs
+        fun syncEngine(): SpecialDatesSyncEngine
+    }
+
+    override suspend fun doWork(): Result {
+        val deps = EntryPointAccessors.fromApplication(applicationContext, Deps::class.java)
+        val prefs = deps.settingsPrefs()
+        // Respect the toggle even for already-queued work; never revive a
+        // disabled feature.
+        if (!prefs.specialDatesEnabled.first()) return Result.success()
+
+        val now = System.currentTimeMillis()
+        // A foreground resume can fire often — skip if we synced recently.
+        val foreground = inputData.getBoolean(SpecialDatesScheduler.INPUT_FOREGROUND, false)
+        if (foreground && now - prefs.specialDatesLastForegroundSync.first() < FOREGROUND_DEBOUNCE_MILLIS) {
+            return Result.success()
+        }
+
+        val today = Clock.System.todayIn(TimeZone.currentSystemDefault())
+        return try {
+            val result = deps.syncEngine().sync(today)
+            val stalled = if (result == SpecialDatesSyncResult.PermissionMissing) {
+                SpecialDatesStalledReason.PermissionRevoked
+            } else {
+                null
+            }
+            prefs.recordSpecialDatesRun(now, stalled)
+            if (foreground) prefs.setSpecialDatesLastForegroundSync(now)
+            Result.success()
+        } catch (e: Exception) {
+            Log.w(TAG, "Special-dates sync failed", e)
+            Result.retry()
+        }
+    }
+
+    companion object {
+        private const val TAG = "SpecialDatesSync"
+
+        /** Skip a foreground-triggered sync if one ran within this window (4h). */
+        private const val FOREGROUND_DEBOUNCE_MILLIS = 4L * 60 * 60 * 1000
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/contacts/SpecialDatesSyncEngine.kt

@@ -0,0 +1,277 @@
+package de.jeanlucmakiola.calendula.data.contacts
+
+import android.provider.CalendarContract
+import de.jeanlucmakiola.calendula.data.calendar.CalendarDataSource
+import de.jeanlucmakiola.calendula.data.calendar.ManagedEventRow
+import de.jeanlucmakiola.calendula.data.calendar.toWriteTimes
+import de.jeanlucmakiola.calendula.data.prefs.CalendarReminderOverride
+import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
+import de.jeanlucmakiola.calendula.data.prefs.resolveDefaultReminder
+import de.jeanlucmakiola.calendula.domain.Availability
+import de.jeanlucmakiola.calendula.domain.EventForm
+import de.jeanlucmakiola.calendula.domain.RecurrenceFreq
+import de.jeanlucmakiola.calendula.domain.SimpleRecurrence
+import de.jeanlucmakiola.calendula.domain.contacts.ContactSpecialDate
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
+import de.jeanlucmakiola.calendula.domain.contacts.anchorDate
+import de.jeanlucmakiola.calendula.domain.contacts.ageAtNextOccurrence
+import de.jeanlucmakiola.calendula.domain.contacts.managedEventUid
+import de.jeanlucmakiola.calendula.domain.contacts.renderSpecialDateTitle
+import de.jeanlucmakiola.calendula.domain.toRRule
+import kotlinx.coroutines.flow.first
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.LocalTime
+import java.time.ZoneId
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/** Outcome of one mirror reconcile, reported back so the worker can record status. */
+enum class SpecialDatesSyncResult { Success, Disabled, PermissionMissing }
+
+/**
+ * Localized, per-type presentation the engine needs but can't derive purely
+ * (calendar display name, colour, and the default title template). Kept behind
+ * an interface so the engine's diff stays unit-testable without Android
+ * resources.
+ */
+interface SpecialDatesCalendarSpec {
+    fun displayName(type: SpecialDateType): String
+    fun color(type: SpecialDateType): Int
+    fun defaultTitleTemplate(type: SpecialDateType): String
+}
+
+/**
+ * Mirrors contact birthdays/anniversaries/custom dates into local calendars,
+ * one per type. Every reconcile is an idempotent diff keyed on the deterministic
+ * `UID_2445` ([managedEventUid]): new contacts are inserted (seeding user-owned
+ * fields once), changed contacts get a *targeted* managed-column update, and
+ * removed contacts are deleted — so a user's own edits (reminders, location,
+ * notes) are never clobbered. See docs/design/contact-special-dates.md.
+ */
+@Singleton
+class SpecialDatesSyncEngine @Inject constructor(
+    private val contacts: ContactSpecialDatesDataSource,
+    private val calendars: CalendarDataSource,
+    private val prefs: SettingsPrefs,
+    private val spec: SpecialDatesCalendarSpec,
+) {
+
+    /**
+     * Reconcile every enabled type against the device's contacts. [today] anchors
+     * the age snapshot. Returns why it stopped early (disabled / permission gone)
+     * or [SpecialDatesSyncResult.Success].
+     */
+    suspend fun sync(today: LocalDate): SpecialDatesSyncResult {
+        if (!prefs.specialDatesEnabled.first()) return SpecialDatesSyncResult.Disabled
+        if (!contacts.hasPermission()) return SpecialDatesSyncResult.PermissionMissing
+
+        val enabledTypes = prefs.specialDatesTypes.first()
+        val calendarByType = reconcileCalendars(enabledTypes)
+
+        val desiredByType = contacts.readSpecialDates().groupBy { it.type }
+        val reminderCtx = readReminderContext()
+        val templates = prefs.specialDatesTitleTemplates.first()
+        val showAge = prefs.specialDatesShowAge.first()
+
+        calendarByType.forEach { (type, calendarId) ->
+            val template = templates[type]?.takeIf { it.isNotBlank() }
+                ?: spec.defaultTitleTemplate(type)
+            syncType(
+                calendarId = calendarId,
+                type = type,
+                contactsOfType = desiredByType[type].orEmpty(),
+                today = today,
+                template = template,
+                showAge = showAge,
+                reminderCtx = reminderCtx,
+            )
+        }
+        return SpecialDatesSyncResult.Success
+    }
+
+    /** Delete every managed calendar and forget its id — used when the feature is turned off. */
+    suspend fun teardown() {
+        calendars.findManagedCalendars().forEach { calendars.deleteCalendar(it.id) }
+        SpecialDateType.entries.forEach { prefs.setSpecialDatesCalendarId(it, null) }
+    }
+
+    /**
+     * Ensure each enabled type has exactly one managed calendar (adopting an
+     * existing one, or the stored id if it still exists, else creating one) and
+     * that disabled types have none. Returns the calendar id per enabled type.
+     */
+    private suspend fun reconcileCalendars(enabledTypes: Set<SpecialDateType>): Map<SpecialDateType, Long> {
+        val foundByType = calendars.findManagedCalendars()
+            .groupBy({ it.type }, { it.id })
+            .mapValues { it.value.first() }
+        val stored = prefs.specialDatesCalendars.first()
+        val result = LinkedHashMap<SpecialDateType, Long>()
+        for (type in SpecialDateType.entries) {
+            // A stored id counts only if the calendar still exists (the user may
+            // have deleted it in system settings); otherwise adopt a found one.
+            val existingId = stored[type]?.takeIf { id -> foundByType.containsValue(id) }
+                ?: foundByType[type]
+            if (type in enabledTypes) {
+                val id = existingId ?: createCalendar(type)
+                if (stored[type] != id) prefs.setSpecialDatesCalendarId(type, id)
+                result[type] = id
+            } else {
+                if (existingId != null) calendars.deleteCalendar(existingId)
+                if (stored.containsKey(type)) prefs.setSpecialDatesCalendarId(type, null)
+            }
+        }
+        return result
+    }
+
+    private suspend fun createCalendar(type: SpecialDateType): Long {
+        val id = calendars.createManagedCalendar(spec.displayName(type), spec.color(type), type)
+        prefs.setSpecialDatesCalendarId(type, id)
+        // Seed a useful all-day reminder default (on the day + a week before), so
+        // birthdays get lead time out of the box. Per-calendar, user-adjustable —
+        // only set when the user hasn't already configured this calendar.
+        if (!prefs.perCalendarAllDayReminderOverride.first().containsKey(id)) {
+            prefs.setCalendarAllDayReminderOverride(
+                id,
+                CalendarReminderOverride.Minutes(DEFAULT_REMINDER_MINUTES),
+            )
+        }
+        return id
+    }
+
+    private suspend fun syncType(
+        calendarId: Long,
+        type: SpecialDateType,
+        contactsOfType: List<ContactSpecialDate>,
+        today: LocalDate,
+        template: String,
+        showAge: Boolean,
+        reminderCtx: ReminderContext,
+    ) {
+        val built = contactsOfType.map { sd ->
+            buildManagedEvent(calendarId, type, sd, today, template, showAge, reminderCtx)
+        }
+        val diff = diffManagedEvents(built.map { it.desired }, calendars.queryManagedEvents(calendarId))
+        val formByUid = built.associate { it.desired.uid to it.form }
+        diff.insertUids.forEach { uid ->
+            calendars.insertManagedEvent(formByUid.getValue(uid), uid, reminderCtx.allDayTimeMinutes)
+        }
+        diff.updates.forEach { calendars.updateManagedFields(it.eventId, it.columns) }
+        diff.deleteEventIds.forEach { calendars.deleteEvent(it) }
+    }
+
+    private fun buildManagedEvent(
+        calendarId: Long,
+        type: SpecialDateType,
+        sd: ContactSpecialDate,
+        today: LocalDate,
+        template: String,
+        showAge: Boolean,
+        reminderCtx: ReminderContext,
+    ): BuiltManagedEvent {
+        val anchor = sd.anchorDate()
+        val start = LocalDateTime(anchor, LocalTime(0, 0))
+        val age = if (showAge) sd.ageAtNextOccurrence(today) else null
+        val title = renderSpecialDateTitle(template, sd.displayName, age)
+        val form = EventForm(
+            calendarId = calendarId,
+            title = title,
+            isAllDay = true,
+            start = start,
+            end = start,
+            reminders = reminderCtx.resolveAllDay(calendarId),
+            availability = Availability.Free,
+            rrule = YEARLY_RRULE,
+        )
+        val dtStartMillis = form.toWriteTimes(ZoneId.systemDefault()).dtStartMillis
+        return BuiltManagedEvent(
+            desired = ManagedEventDesired(
+                uid = managedEventUid(type, sd.lookupKey),
+                title = title,
+                dtStartMillis = dtStartMillis,
+                rrule = YEARLY_RRULE,
+            ),
+            form = form,
+        )
+    }
+
+    private suspend fun readReminderContext(): ReminderContext = ReminderContext(
+        timedGlobal = prefs.defaultReminderMinutes.first(),
+        allDayGlobal = prefs.defaultAllDayReminderMinutes.first(),
+        timedOverrides = prefs.perCalendarReminderOverride.first(),
+        allDayOverrides = prefs.perCalendarAllDayReminderOverride.first(),
+        allDayTimeMinutes = prefs.allDayReminderTimeMinutes.first(),
+    )
+
+    private data class ReminderContext(
+        val timedGlobal: List<Int>,
+        val allDayGlobal: List<Int>,
+        val timedOverrides: Map<Long, List<Int>>,
+        val allDayOverrides: Map<Long, List<Int>>,
+        val allDayTimeMinutes: Int,
+    ) {
+        fun resolveAllDay(calendarId: Long): List<Int> = resolveDefaultReminder(
+            timedGlobal = timedGlobal,
+            allDayGlobal = allDayGlobal,
+            timedOverrides = timedOverrides,
+            allDayOverrides = allDayOverrides,
+            calendarId = calendarId,
+            isAllDay = true,
+        )
+    }
+
+    private data class BuiltManagedEvent(val desired: ManagedEventDesired, val form: EventForm)
+
+    private companion object {
+        /** "On the day" (0) + one week before (7 days), as all-day lead minutes. */
+        val DEFAULT_REMINDER_MINUTES = listOf(0, 7 * 24 * 60)
+        val YEARLY_RRULE = SimpleRecurrence(freq = RecurrenceFreq.Yearly).toRRule()
+    }
+}
+
+/** The managed columns of a desired event, compared against the existing row. */
+internal data class ManagedEventDesired(
+    val uid: String,
+    val title: String,
+    val dtStartMillis: Long,
+    val rrule: String?,
+)
+
+internal data class ManagedFieldUpdate(val eventId: Long, val columns: Map<String, Any?>)
+
+internal data class ManagedDiff(
+    val insertUids: List<String>,
+    val updates: List<ManagedFieldUpdate>,
+    val deleteEventIds: List<Long>,
+)
+
+/**
+ * The idempotent diff at the heart of the mirror, keyed on `UID_2445`:
+ * desired-not-existing → insert, existing-not-desired → delete, and for events
+ * in both only the *changed* managed columns (title/dtstart/rrule) are emitted —
+ * so a re-run with no contact changes produces nothing, and a managed update
+ * never touches user-owned columns or reminder rows. Pure, so it's unit-tested.
+ */
+internal fun diffManagedEvents(
+    desired: List<ManagedEventDesired>,
+    existing: List<ManagedEventRow>,
+): ManagedDiff {
+    val desiredByUid = desired.associateBy { it.uid }
+    val existingByUid = existing.associateBy { it.uid }
+    val insertUids = desired.filter { it.uid !in existingByUid }.map { it.uid }
+    val deleteEventIds = existing.filter { it.uid !in desiredByUid }.map { it.eventId }
+    val updates = buildList {
+        for (d in desired) {
+            val row = existingByUid[d.uid] ?: continue
+            val columns = buildMap<String, Any?> {
+                if (row.title != d.title) put(CalendarContract.Events.TITLE, d.title)
+                if (row.dtStartMillis != d.dtStartMillis) {
+                    put(CalendarContract.Events.DTSTART, d.dtStartMillis)
+                }
+                if (row.rrule != d.rrule) put(CalendarContract.Events.RRULE, d.rrule)
+            }
+            if (columns.isNotEmpty()) add(ManagedFieldUpdate(row.eventId, columns))
+        }
+    }
+    return ManagedDiff(insertUids, updates, deleteEventIds)
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/di/DataModule.kt

@@ -14,6 +14,10 @@ import de.jeanlucmakiola.calendula.data.calendar.AndroidCalendarDataSource
 import de.jeanlucmakiola.calendula.data.calendar.CalendarDataSource
 import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
 import de.jeanlucmakiola.calendula.data.calendar.CalendarRepositoryImpl
+import de.jeanlucmakiola.calendula.data.contacts.AndroidContactSpecialDatesDataSource
+import de.jeanlucmakiola.calendula.data.contacts.AndroidSpecialDatesCalendarSpec
+import de.jeanlucmakiola.calendula.data.contacts.ContactSpecialDatesDataSource
+import de.jeanlucmakiola.calendula.data.contacts.SpecialDatesCalendarSpec
 import de.jeanlucmakiola.calendula.data.reminders.AndroidReminderAlertStore
 import de.jeanlucmakiola.calendula.data.reminders.ReminderAlertStore
 import kotlinx.coroutines.CoroutineDispatcher
@@ -45,6 +49,18 @@ abstract class DataBindModule {
     abstract fun bindReminderAlertStore(
         impl: AndroidReminderAlertStore,
     ): ReminderAlertStore
+
+    @Binds
+    @Singleton
+    abstract fun bindContactSpecialDatesDataSource(
+        impl: AndroidContactSpecialDatesDataSource,
+    ): ContactSpecialDatesDataSource
+
+    @Binds
+    @Singleton
+    abstract fun bindSpecialDatesCalendarSpec(
+        impl: AndroidSpecialDatesCalendarSpec,
+    ): SpecialDatesCalendarSpec
 }
 
 @Module

app/src/main/java/de/jeanlucmakiola/calendula/data/prefs/SettingsPrefs.kt

@@ -8,6 +8,7 @@ import androidx.datastore.preferences.core.intPreferencesKey
 import androidx.datastore.preferences.core.longPreferencesKey
 import androidx.datastore.preferences.core.stringPreferencesKey
 import de.jeanlucmakiola.calendula.domain.EventFormField
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
 import de.jeanlucmakiola.calendula.ui.agenda.AgendaRange
 import de.jeanlucmakiola.calendula.ui.agenda.parseAgendaRange
 import de.jeanlucmakiola.calendula.ui.agenda.storageValue
@@ -427,6 +428,95 @@ class SettingsPrefs @Inject constructor(
         }
     }
 
+    // --- Contact special dates (issue #15) ------------------------------
+
+    /** Master switch for the contact special-dates mirror. Default OFF (opt-in). */
+    val specialDatesEnabled: Flow<Boolean> = store.data.map { it[SPECIAL_DATES_ENABLED_KEY] ?: false }
+
+    suspend fun setSpecialDatesEnabled(enabled: Boolean) {
+        store.edit { it[SPECIAL_DATES_ENABLED_KEY] = enabled }
+    }
+
+    /** The date types the user wants mirrored (default: all three). */
+    val specialDatesTypes: Flow<Set<SpecialDateType>> = store.data.map { prefs ->
+        SpecialDateType.entries.filterTo(mutableSetOf()) { prefs[typeEnabledKey(it)] ?: true }
+    }
+
+    suspend fun setSpecialDateTypeEnabled(type: SpecialDateType, enabled: Boolean) {
+        store.edit { it[typeEnabledKey(type)] = enabled }
+    }
+
+    /** The managed calendar id per type, for the ones that currently exist. */
+    val specialDatesCalendars: Flow<Map<SpecialDateType, Long>> = store.data.map { prefs ->
+        SpecialDateType.entries.mapNotNull { type ->
+            prefs[calendarIdKey(type)]?.let { type to it }
+        }.toMap()
+    }
+
+    /** Every managed calendar id — the editor locks title/date/recurrence for their events. */
+    val managedCalendarIds: Flow<Set<Long>> = specialDatesCalendars.map { it.values.toSet() }
+
+    suspend fun setSpecialDatesCalendarId(type: SpecialDateType, calendarId: Long?) {
+        store.edit { prefs ->
+            if (calendarId == null) prefs.remove(calendarIdKey(type)) else prefs[calendarIdKey(type)] = calendarId
+        }
+    }
+
+    /**
+     * The title template per type ("{name}'s birthday"); an empty string means
+     * unset, so the settings screen can seed the localized default. `{name}` is
+     * the contact name, `{age}` the age at the upcoming date (empty when the
+     * birth year is unknown or [specialDatesShowAge] is off).
+     */
+    val specialDatesTitleTemplates: Flow<Map<SpecialDateType, String>> = store.data.map { prefs ->
+        SpecialDateType.entries.associateWith { prefs[titleTemplateKey(it)].orEmpty() }
+    }
+
+    suspend fun setSpecialDatesTitleTemplate(type: SpecialDateType, template: String) {
+        store.edit { it[titleTemplateKey(type)] = template }
+    }
+
+    /** Whether `{age}` resolves in the title (only meaningful when the year is known). Default ON. */
+    val specialDatesShowAge: Flow<Boolean> = store.data.map { it[SPECIAL_DATES_SHOW_AGE_KEY] ?: true }
+
+    suspend fun setSpecialDatesShowAge(enabled: Boolean) {
+        store.edit { it[SPECIAL_DATES_SHOW_AGE_KEY] = enabled }
+    }
+
+    /** Outcome of the last mirror sync, for the settings status line. */
+    val specialDatesStatus: Flow<SpecialDatesStatus> = store.data.map { prefs ->
+        SpecialDatesStatus(
+            lastRun = prefs[SPECIAL_DATES_LAST_RUN_KEY] ?: 0L,
+            stalled = prefs[SPECIAL_DATES_STALLED_KEY]
+                ?.let { name -> SpecialDatesStalledReason.entries.firstOrNull { it.name == name } },
+        )
+    }
+
+    /** Record a sync outcome; [stalled] non-null marks the feature paused (e.g. permission revoked). */
+    suspend fun recordSpecialDatesRun(atMillis: Long, stalled: SpecialDatesStalledReason?) {
+        store.edit { prefs ->
+            prefs[SPECIAL_DATES_LAST_RUN_KEY] = atMillis
+            if (stalled == null) prefs.remove(SPECIAL_DATES_STALLED_KEY) else prefs[SPECIAL_DATES_STALLED_KEY] = stalled.name
+        }
+    }
+
+    /** Epoch millis of the last foreground-triggered sync, to debounce ON_RESUME. */
+    val specialDatesLastForegroundSync: Flow<Long> =
+        store.data.map { it[SPECIAL_DATES_LAST_FG_SYNC_KEY] ?: 0L }
+
+    suspend fun setSpecialDatesLastForegroundSync(atMillis: Long) {
+        store.edit { it[SPECIAL_DATES_LAST_FG_SYNC_KEY] = atMillis }
+    }
+
+    private fun typeEnabledKey(type: SpecialDateType) =
+        booleanPreferencesKey("special_dates_type_${type.name}")
+
+    private fun calendarIdKey(type: SpecialDateType) =
+        longPreferencesKey("special_dates_calendar_${type.name}")
+
+    private fun titleTemplateKey(type: SpecialDateType) =
+        stringPreferencesKey("special_dates_title_${type.name}")
+
     private fun parseFormFields(stored: String?): Set<EventFormField> = when (stored) {
         null -> DEFAULT_FORM_FIELDS
         else -> stored.split(',')
@@ -479,9 +569,30 @@ class SettingsPrefs @Inject constructor(
         const val DEFAULT_BACKUP_INTERVAL = 1_440L
         /** Floor for the automatic-backup interval (also above WorkManager's 15-min limit). */
         const val MIN_BACKUP_INTERVAL = 30L
+
+        internal val SPECIAL_DATES_ENABLED_KEY = booleanPreferencesKey("special_dates_enabled")
+        internal val SPECIAL_DATES_SHOW_AGE_KEY = booleanPreferencesKey("special_dates_show_age")
+        internal val SPECIAL_DATES_LAST_RUN_KEY = longPreferencesKey("special_dates_last_run")
+        internal val SPECIAL_DATES_STALLED_KEY = stringPreferencesKey("special_dates_stalled_reason")
+        internal val SPECIAL_DATES_LAST_FG_SYNC_KEY =
+            longPreferencesKey("special_dates_last_foreground_sync")
     }
 }
 
+/** Snapshot of the special-dates mirror's last outcome (see [SettingsPrefs.specialDatesStatus]). */
+data class SpecialDatesStatus(
+    /** Epoch millis of the last sync, or 0 if it has never run. */
+    val lastRun: Long,
+    /** Non-null when the mirror is paused and why; null when healthy. */
+    val stalled: SpecialDatesStalledReason?,
+)
+
+/** Why the special-dates mirror is paused. */
+enum class SpecialDatesStalledReason {
+    /** READ_CONTACTS was revoked in system settings after the feature was enabled. */
+    PermissionRevoked,
+}
+
 /** Snapshot of the automatic backup's last outcome (see [SettingsPrefs.autoBackupStatus]). */
 data class BackupStatus(
     /** Epoch millis of the last run, or 0 if it has never run. */

app/src/main/java/de/jeanlucmakiola/calendula/domain/contacts/ContactSpecialDate.kt

@@ -0,0 +1,122 @@
+package de.jeanlucmakiola.calendula.domain.contacts
+
+import java.time.LocalDate
+
+/**
+ * The kinds of contact "special date" Calendula mirrors into local calendars.
+ * Each kind gets its own local calendar, so it inherits per-calendar colour,
+ * visibility and reminder defaults for free. See
+ * docs/design/contact-special-dates.md.
+ */
+enum class SpecialDateType {
+    Birthday,
+    Anniversary,
+
+    /** Everything else — a contact "Event" that is neither birthday nor anniversary. */
+    Custom,
+}
+
+/**
+ * One dated event read from a device contact (a `ContactsContract` `Event`
+ * row). The [lookupKey] is the stable contact identity used to reconcile the
+ * mirror without duplicating; [year] is null when the contact stored the date
+ * without one (`--MM-dd`), in which case age can't be shown.
+ */
+data class ContactSpecialDate(
+    val lookupKey: String,
+    val displayName: String,
+    val type: SpecialDateType,
+    val month: Int,
+    val day: Int,
+    val year: Int?,
+    /** The contact's custom label for a [SpecialDateType.Custom] date, if any. */
+    val label: String? = null,
+)
+
+/** The parsed month/day (+ optional year) of a contact date. */
+data class ContactDateParts(val year: Int?, val month: Int, val day: Int)
+
+/**
+ * A fixed leap year to validate and anchor year-less dates against, so that a
+ * `--02-29` birthday is representable (and, once anchored, only recurs in leap
+ * years — matching how the calendar provider expands a yearly Feb-29 series).
+ */
+const val YEARLESS_ANCHOR_YEAR = 1972
+
+/**
+ * Parse a `ContactsContract.CommonDataKinds.Event.START_DATE` value into its
+ * calendar parts, or null if it isn't a usable date. Handles the three shapes
+ * seen in the wild:
+ * - full `yyyy-MM-dd` (year known),
+ * - year-less `--MM-dd` (year null),
+ * - compact `yyyyMMdd`.
+ *
+ * A date that names an impossible day (e.g. `1999-02-29`) is rejected. Pure, so
+ * it's unit-tested without a device.
+ */
+fun parseContactEventDate(raw: String?): ContactDateParts? {
+    val s = raw?.trim().orEmpty()
+    if (s.isEmpty()) return null
+
+    // Year-less: "--MM-dd" or "--MMdd".
+    if (s.startsWith("--")) {
+        val (m, d) = parseMonthDay(s.substring(2)) ?: return null
+        return validated(null, m, d)
+    }
+
+    if (s.contains('-')) {
+        val parts = s.split('-').filter { it.isNotEmpty() }
+        return when (parts.size) {
+            // "yyyy-MM-dd" — but a leading '-' would have dropped the empty
+            // first part, so require the first token to look like a year.
+            3 -> if (s.startsWith('-')) null else validated(
+                year = parts[0].toIntOrNull() ?: return null,
+                month = parts[1].toIntOrNull() ?: return null,
+                day = parts[2].toIntOrNull() ?: return null,
+            )
+            // Year-less "MM-dd" without the "--" prefix.
+            2 -> validated(
+                year = null,
+                month = parts[0].toIntOrNull() ?: return null,
+                day = parts[1].toIntOrNull() ?: return null,
+            )
+            else -> null
+        }
+    }
+
+    // Compact "yyyyMMdd".
+    if (s.length == 8 && s.all { it.isDigit() }) {
+        return validated(
+            year = s.substring(0, 4).toInt(),
+            month = s.substring(4, 6).toInt(),
+            day = s.substring(6, 8).toInt(),
+        )
+    }
+
+    return null
+}
+
+/** "MM-dd" or compact "MMdd". */
+private fun parseMonthDay(rest: String): Pair<Int, Int>? {
+    if (rest.contains('-')) {
+        val p = rest.split('-').filter { it.isNotEmpty() }
+        if (p.size != 2) return null
+        return (p[0].toIntOrNull() ?: return null) to (p[1].toIntOrNull() ?: return null)
+    }
+    if (rest.length == 4 && rest.all { it.isDigit() }) {
+        return rest.substring(0, 2).toInt() to rest.substring(2, 4).toInt()
+    }
+    return null
+}
+
+/**
+ * Confirm month/day form a real calendar date (validated against the actual
+ * year when known, otherwise the leap anchor so `02-29` survives).
+ */
+private fun validated(year: Int?, month: Int, day: Int): ContactDateParts? {
+    if (month !in 1..12 || day !in 1..31) return null
+    val checkYear = year ?: YEARLESS_ANCHOR_YEAR
+    return runCatching { LocalDate.of(checkYear, month, day) }
+        .map { ContactDateParts(year, month, day) }
+        .getOrNull()
+}

app/src/main/java/de/jeanlucmakiola/calendula/domain/contacts/SpecialDateFormatting.kt

@@ -0,0 +1,50 @@
+package de.jeanlucmakiola.calendula.domain.contacts
+
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.number
+
+/**
+ * The deterministic `Events.UID_2445` that ties a mirrored event to its source
+ * contact date. Stable across syncs (the reconciliation key), and namespaced by
+ * type so the same contact's birthday and anniversary never collide.
+ */
+fun managedEventUid(type: SpecialDateType, lookupKey: String): String =
+    "contact-${type.name.lowercase()}:$lookupKey@calendula"
+
+/**
+ * The all-day date the recurring `FREQ=YEARLY` series is anchored at: the real
+ * date when the year is known (so age can be derived), otherwise the month/day
+ * on a fixed leap anchor year so a `--02-29` date stays representable and the
+ * anchor never drifts between syncs.
+ */
+fun ContactSpecialDate.anchorDate(): LocalDate =
+    LocalDate(year ?: YEARLESS_ANCHOR_YEAR, month, day)
+
+/**
+ * The age the contact reaches on the *upcoming* occurrence of this date,
+ * relative to [today], or null when the year is unknown. Because a
+ * `FREQ=YEARLY` event carries a single static title, this is a snapshot taken
+ * at sync time (refreshed on the next sync), not a per-occurrence value.
+ */
+fun ContactSpecialDate.ageAtNextOccurrence(today: LocalDate): Int? {
+    val birthYear = year ?: return null
+    val monthDayPassedThisYear = month < today.month.number ||
+        (month == today.month.number && day < today.day)
+    val nextYear = if (monthDayPassedThisYear) today.year + 1 else today.year
+    return nextYear - birthYear
+}
+
+/**
+ * Render a title [template] for a contact, substituting `{name}` and `{age}`
+ * (the latter empty when [age] is null). Collapses the whitespace the empty
+ * `{age}` may leave behind, so "{name}'s birthday ({age})" degrades cleanly to
+ * "Jane's birthday" when no year is known.
+ */
+fun renderSpecialDateTitle(template: String, name: String, age: Int?): String =
+    template
+        .replace("{name}", name)
+        .replace("{age}", age?.toString().orEmpty())
+        // Drop an empty "()" left by an unresolved {age}, then tidy spacing.
+        .replace(Regex("""\(\s*\)"""), "")
+        .replace(Regex("""\s+"""), " ")
+        .trim()

app/src/main/java/de/jeanlucmakiola/calendula/ui/RootScreen.kt

@@ -19,6 +19,7 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.core.content.ContextCompat
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleEventObserver
+import de.jeanlucmakiola.calendula.data.contacts.SpecialDatesScheduler
 import de.jeanlucmakiola.calendula.ui.permission.PermissionScreen
 import de.jeanlucmakiola.calendula.ui.permission.ReminderOnboardingScreen
 import de.jeanlucmakiola.calendula.ui.permission.ReminderOnboardingViewModel
@@ -49,6 +50,15 @@ fun RootScreen(
                 hasPermission = ContextCompat.checkSelfPermission(
                     context, Manifest.permission.READ_CALENDAR
                 ) == PackageManager.PERMISSION_GRANTED
+                // Refresh the contact special-dates mirror on foreground (the
+                // worker is debounced and no-ops when the feature is off). Gated
+                // on the permission so users without the opt-in never enqueue it.
+                if (ContextCompat.checkSelfPermission(
+                        context, Manifest.permission.READ_CONTACTS
+                    ) == PackageManager.PERMISSION_GRANTED
+                ) {
+                    SpecialDatesScheduler.runNow(context, foreground = true)
+                }
             }
         }
         lifecycle.addObserver(obs)

app/src/main/java/de/jeanlucmakiola/calendula/ui/common/InlineTextField.kt

@@ -36,6 +36,7 @@ fun InlineTextField(
     textStyle: TextStyle = MaterialTheme.typography.titleMedium,
     singleLine: Boolean = true,
     minLines: Int = 1,
+    enabled: Boolean = true,
     keyboardType: KeyboardType = KeyboardType.Text,
     capitalization: KeyboardCapitalization = KeyboardCapitalization.None,
     imeAction: ImeAction = ImeAction.Default,
@@ -43,15 +44,17 @@ fun InlineTextField(
     onImeAction: (() -> Unit)? = null,
 ) {
     val resolvedStyle = textStyle.copy(
-        color = if (textStyle.color.isSpecified) {
-            textStyle.color
-        } else {
-            MaterialTheme.colorScheme.onSurface
+        color = when {
+            // A disabled field reads as dimmed, like a locked value.
+            !enabled -> MaterialTheme.colorScheme.onSurfaceVariant
+            textStyle.color.isSpecified -> textStyle.color
+            else -> MaterialTheme.colorScheme.onSurface
         },
     )
     BasicTextField(
         value = value,
         onValueChange = onValueChange,
+        enabled = enabled,
         textStyle = resolvedStyle,
         singleLine = singleLine,
         minLines = minLines,

app/src/main/java/de/jeanlucmakiola/calendula/ui/edit/EventEditScreen.kt

@@ -435,6 +435,10 @@ private fun EventEditContent(
     val form = state.form
     val locale = currentLocale()
     val dark = isSystemInDarkTheme()
+    // The title, date and recurrence are managed by the special-dates sync, so
+    // they're locked here; everything else (reminders, location, notes) is the
+    // user's to edit.
+    val locked = state.isManaged
     var picker by remember { mutableStateOf<PickerTarget?>(null) }
     var showCalendarPicker by rememberSaveable { mutableStateOf(false) }
     var showReminderPicker by rememberSaveable { mutableStateOf(false) }
@@ -519,6 +523,7 @@ private fun EventEditContent(
             placeholder = stringResource(R.string.event_edit_title_hint),
             textStyle = MaterialTheme.typography.headlineMedium
                 .copy(fontWeight = FontWeight.SemiBold),
+            enabled = !locked,
             modifier = Modifier
                 .fillMaxWidth()
                 .padding(vertical = 4.dp)
@@ -531,6 +536,17 @@ private fun EventEditContent(
                 .height(3.dp)
                 .background(accent, RoundedCornerShape(2.dp)),
         )
+        if (locked) {
+            Spacer(Modifier.height(10.dp))
+            Text(
+                text = stringResource(
+                    R.string.event_edit_managed_hint,
+                    selectedCalendar?.displayName.orEmpty(),
+                ),
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
 
         Spacer(Modifier.height(20.dp))
 
@@ -549,7 +565,11 @@ private fun EventEditContent(
                         style = MaterialTheme.typography.titleMedium,
                         modifier = Modifier.weight(1f),
                     )
-                    Switch(checked = form.isAllDay, onCheckedChange = viewModel::setAllDay)
+                    Switch(
+                        checked = form.isAllDay,
+                        onCheckedChange = viewModel::setAllDay,
+                        enabled = !locked,
+                    )
                 }
             },
         ) {
@@ -561,6 +581,7 @@ private fun EventEditContent(
                 locale = locale,
                 onDateClick = { picker = PickerTarget.StartDate },
                 onTimeClick = { picker = PickerTarget.StartTime },
+                enabled = !locked,
             )
             ScheduleRow(
                 label = stringResource(R.string.event_edit_ends),
@@ -570,6 +591,7 @@ private fun EventEditContent(
                 onDateClick = { picker = PickerTarget.EndDate },
                 onTimeClick = { picker = PickerTarget.EndTime },
                 isError = EventFormProblem.EndBeforeStart in state.problems,
+                enabled = !locked,
             )
             if (EventFormProblem.EndBeforeStart in state.problems) {
                 Spacer(Modifier.height(2.dp))
@@ -700,7 +722,7 @@ private fun EventEditContent(
             EditCard(
                 icon = Icons.Default.Repeat,
                 iconContentDescription = null,
-                onClick = { showRecurrencePicker = true },
+                onClick = if (locked) null else ({ showRecurrencePicker = true }),
             ) {
                 Row(
                     verticalAlignment = Alignment.CenterVertically,
@@ -1858,6 +1880,7 @@ private fun InlineField(
     textStyle: TextStyle = MaterialTheme.typography.titleMedium,
     singleLine: Boolean = true,
     minLines: Int = 1,
+    enabled: Boolean = true,
     keyboardType: KeyboardType = KeyboardType.Text,
     modifier: Modifier = Modifier
         .fillMaxWidth()
@@ -1871,6 +1894,7 @@ private fun InlineField(
         textStyle = textStyle,
         singleLine = singleLine,
         minLines = minLines,
+        enabled = enabled,
         keyboardType = keyboardType,
     )
 }
@@ -1885,6 +1909,7 @@ private fun ScheduleRow(
     onDateClick: () -> Unit,
     onTimeClick: () -> Unit,
     isError: Boolean = false,
+    enabled: Boolean = true,
 ) {
     val dateFormat = remember(locale) {
         DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM).withLocale(locale)
@@ -1894,11 +1919,12 @@ private fun ScheduleRow(
         timeOfDayFormatter(use24Hour, locale)
     }
     // Tappable values read as links (primary), like the location on the
-    // detail screen; errors flip them to the error colour.
-    val valueColor = if (isError) {
-        MaterialTheme.colorScheme.error
-    } else {
-        MaterialTheme.colorScheme.primary
+    // detail screen; errors flip them to the error colour; a locked (managed)
+    // row dims to a plain, non-tappable value.
+    val valueColor = when {
+        !enabled -> MaterialTheme.colorScheme.onSurfaceVariant
+        isError -> MaterialTheme.colorScheme.error
+        else -> MaterialTheme.colorScheme.primary
     }
     Row(
         verticalAlignment = Alignment.CenterVertically,
@@ -1915,7 +1941,7 @@ private fun ScheduleRow(
             style = MaterialTheme.typography.titleMedium,
             color = valueColor,
             modifier = Modifier
-                .clickable(onClick = onDateClick)
+                .clickable(enabled = enabled, onClick = onDateClick)
                 .padding(vertical = 8.dp, horizontal = 6.dp),
         )
         if (!isAllDay) {
@@ -1924,7 +1950,7 @@ private fun ScheduleRow(
                 style = MaterialTheme.typography.titleMedium,
                 color = valueColor,
                 modifier = Modifier
-                    .clickable(onClick = onTimeClick)
+                    .clickable(enabled = enabled, onClick = onTimeClick)
                     .padding(vertical = 8.dp, horizontal = 6.dp),
             )
         }

app/src/main/java/de/jeanlucmakiola/calendula/ui/edit/EventEditUiState.kt

@@ -29,6 +29,12 @@ data class EventEditUiState(
     val hiddenFields: List<EventFormField> = emptyList(),
     /** True while editing an existing event (the calendar is then fixed). */
     val isEditing: Boolean = false,
+    /**
+     * True when the event's calendar is a contact special-dates calendar the app
+     * manages. While editing such an event the title, date and recurrence are
+     * locked (sync overwrites them); reminders, location and notes stay editable.
+     */
+    val isManaged: Boolean = false,
     /**
      * Whether to focus the title and raise the keyboard when this is a fresh
      * create form (issue #10). Mirrors the settings flag; the screen only acts

app/src/main/java/de/jeanlucmakiola/calendula/ui/edit/EventEditViewModel.kt

@@ -165,7 +165,8 @@ class EventEditViewModel @Inject constructor(
             ::ExternalInputs,
         ).flowOn(io),
         colorPalette,
-    ) { local, external, palette ->
+        settingsPrefs.managedCalendarIds,
+    ) { local, external, palette, managedIds ->
         val form = local.form ?: return@combine null
         val resolvedId = form.calendarId
             ?: external.lastUsed?.takeIf { id -> external.writable.any { it.id == id } }
@@ -180,6 +181,8 @@ class EventEditViewModel @Inject constructor(
             visibleFields = visibleFields,
             hiddenFields = (EventFormField.entries.toSet() - visibleFields).sorted(),
             isEditing = local.editTarget != null,
+            // Editing an event in a managed calendar locks its synced fields.
+            isManaged = local.editTarget != null && resolvedId != null && resolvedId in managedIds,
             autofocusTitle = external.autofocusTitle,
             // A modified-occurrence exception can't carry its own rule, so
             // the scope dialog drops "only this event" after a rule change.

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsScreen.kt

@@ -38,6 +38,7 @@ import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.BugReport
+import androidx.compose.material.icons.filled.Cake
 import androidx.compose.material.icons.filled.CalendarMonth
 import androidx.compose.material.icons.filled.Dashboard
 import androidx.compose.material.icons.filled.Check
@@ -91,6 +92,7 @@ import de.jeanlucmakiola.calendula.data.prefs.ThemeMode
 import de.jeanlucmakiola.calendula.data.prefs.TimeFormatPref
 import de.jeanlucmakiola.calendula.data.prefs.WeekStartPref
 import de.jeanlucmakiola.calendula.domain.EventFormField
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
 import de.jeanlucmakiola.calendula.qs.NewEventTileService
 import de.jeanlucmakiola.calendula.ui.crash.CrashReportDialog
 import de.jeanlucmakiola.calendula.ui.crash.openIssueTracker
@@ -121,7 +123,7 @@ import java.time.format.TextStyle as JavaTextStyle
 import java.util.Calendar
 
 /** The settings sub-screens reached from the hub's category rows. */
-private enum class SettingsSection { Appearance, EventForm, Notifications }
+private enum class SettingsSection { Appearance, EventForm, Notifications, SpecialDates }
 
 /**
  * Token-based accent for a leading icon chip (container / on-container pair).
@@ -180,6 +182,13 @@ fun SettingsScreen(
         ) {
             NotificationsScreen(state = state, viewModel = viewModel, onBack = { section = null })
         }
+        AnimatedVisibility(
+            visible = section == SettingsSection.SpecialDates,
+            enter = slideInHorizontally(slideSpec) { it } + fadeIn(),
+            exit = slideOutHorizontally(slideSpec) { it } + fadeOut(),
+        ) {
+            SpecialDatesScreen(viewModel = viewModel, onBack = { section = null })
+        }
     }
 }
 
@@ -225,6 +234,13 @@ private fun SettingsHub(
             leading = { CategoryIcon(Icons.Default.CalendarMonth, ChipAccent.Tertiary) },
             onClick = onManageCalendars,
         )
+        GroupedRow(
+            title = stringResource(R.string.settings_section_special_dates),
+            summary = stringResource(R.string.settings_special_dates_subtitle),
+            position = Position.Middle,
+            leading = { CategoryIcon(Icons.Default.Cake, ChipAccent.Tertiary) },
+            onClick = { onOpenSection(SettingsSection.SpecialDates) },
+        )
         LanguageRow(position = Position.Middle)
         // One-tap add of the "New event" Quick Settings tile. The system prompt
         // is API 33+; on older versions the tile is still addable manually from
@@ -1025,6 +1041,257 @@ private fun NotificationsScreen(
     }
 }
 
+// ---------------------------------------------------------------------------
+// Contact special dates (issue #15)
+// ---------------------------------------------------------------------------
+
+@Composable
+private fun SpecialDatesScreen(
+    viewModel: SettingsViewModel,
+    onBack: () -> Unit,
+) {
+    val state by viewModel.specialDatesState.collectAsStateWithLifecycle()
+    val context = LocalContext.current
+
+    // READ_CONTACTS is requested only here, on enable — never at startup. On a
+    // grant we either enable (if turning on) or just re-sync (clearing a stalled
+    // banner after the permission was re-granted).
+    val permissionLauncher = rememberLauncherForActivityResult(
+        contract = ActivityResultContracts.RequestPermission(),
+    ) { granted ->
+        if (granted) {
+            if (!state.enabled) viewModel.setSpecialDatesEnabled(true) else viewModel.syncSpecialDatesNow()
+        }
+    }
+    val requestOrEnable: () -> Unit = {
+        if (hasContactsPermission(context)) {
+            viewModel.setSpecialDatesEnabled(true)
+        } else {
+            permissionLauncher.launch(Manifest.permission.READ_CONTACTS)
+        }
+    }
+
+    var confirmDisableAll by remember { mutableStateOf(false) }
+    var confirmDisableType by remember { mutableStateOf<SpecialDateType?>(null) }
+    var editTemplate by remember { mutableStateOf<SpecialDateType?>(null) }
+
+    CollapsingScaffold(
+        title = stringResource(R.string.settings_section_special_dates),
+        onBack = onBack,
+    ) {
+        // Paused banner: the permission was revoked after enabling.
+        if (state.enabled && state.stalledPermission) {
+            Surface(
+                shape = RoundedCornerShape(16.dp),
+                color = MaterialTheme.colorScheme.errorContainer,
+                modifier = Modifier.fillMaxWidth(),
+            ) {
+                Column(Modifier.padding(16.dp)) {
+                    Text(
+                        text = stringResource(R.string.settings_special_dates_paused_title),
+                        style = MaterialTheme.typography.titleSmall,
+                        color = MaterialTheme.colorScheme.onErrorContainer,
+                    )
+                    Text(
+                        text = stringResource(R.string.settings_special_dates_paused_hint),
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.onErrorContainer,
+                    )
+                    Spacer(Modifier.height(8.dp))
+                    FilledTonalButton(
+                        onClick = { permissionLauncher.launch(Manifest.permission.READ_CONTACTS) },
+                    ) { Text(stringResource(R.string.settings_special_dates_grant)) }
+                }
+            }
+            Spacer(Modifier.height(16.dp))
+        }
+
+        GroupedRow(
+            title = stringResource(R.string.settings_special_dates_enable),
+            summary = stringResource(R.string.settings_special_dates_enable_hint),
+            position = Position.Alone,
+            trailing = {
+                Switch(
+                    checked = state.enabled,
+                    onCheckedChange = { want -> if (want) requestOrEnable() else confirmDisableAll = true },
+                )
+            },
+            onClick = { if (state.enabled) confirmDisableAll = true else requestOrEnable() },
+        )
+
+        if (state.enabled) {
+            Spacer(Modifier.height(24.dp))
+            // Per-type toggles + their title templates.
+            SpecialDateType.entries.forEachIndexed { index, type ->
+                val on = type in state.types
+                GroupedRow(
+                    title = stringResource(specialDateTypeLabel(type)),
+                    position = if (index == 0) Position.Top else Position.Middle,
+                    trailing = {
+                        Switch(
+                            checked = on,
+                            onCheckedChange = { want ->
+                                if (want) viewModel.setSpecialDateTypeEnabled(type, true)
+                                else confirmDisableType = type
+                            },
+                        )
+                    },
+                    onClick = {
+                        if (on) confirmDisableType = type else viewModel.setSpecialDateTypeEnabled(type, true)
+                    },
+                )
+            }
+            GroupedRow(
+                title = stringResource(R.string.settings_special_dates_template),
+                summary = state.titleTemplates[SpecialDateType.Birthday].orEmpty(),
+                position = Position.Bottom,
+                onClick = { editTemplate = SpecialDateType.Birthday },
+            )
+
+            Spacer(Modifier.height(24.dp))
+            GroupedRow(
+                title = stringResource(R.string.settings_special_dates_show_age),
+                summary = stringResource(R.string.settings_special_dates_show_age_hint),
+                position = Position.Top,
+                trailing = {
+                    Switch(
+                        checked = state.showAge,
+                        onCheckedChange = viewModel::setSpecialDatesShowAge,
+                    )
+                },
+                onClick = { viewModel.setSpecialDatesShowAge(!state.showAge) },
+            )
+            GroupedRow(
+                title = stringResource(R.string.settings_special_dates_sync_now),
+                summary = specialDatesLastRunLabel(context, state.lastRun),
+                position = Position.Bottom,
+                onClick = viewModel::syncSpecialDatesNow,
+            )
+
+            Spacer(Modifier.height(24.dp))
+            Text(
+                text = stringResource(R.string.settings_special_dates_calendar_hint),
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.padding(horizontal = 16.dp),
+            )
+        }
+    }
+
+    if (confirmDisableAll) {
+        SpecialDatesDisableDialog(
+            message = stringResource(R.string.settings_special_dates_disable_all_message),
+            onConfirm = { viewModel.setSpecialDatesEnabled(false); confirmDisableAll = false },
+            onDismiss = { confirmDisableAll = false },
+        )
+    }
+    confirmDisableType?.let { type ->
+        SpecialDatesDisableDialog(
+            message = stringResource(
+                R.string.settings_special_dates_disable_type_message,
+                stringResource(specialDateTypeLabel(type)),
+            ),
+            onConfirm = { viewModel.setSpecialDateTypeEnabled(type, false); confirmDisableType = null },
+            onDismiss = { confirmDisableType = null },
+        )
+    }
+    editTemplate?.let { type ->
+        SpecialDatesTemplateDialog(
+            initial = state.titleTemplates[type].orEmpty(),
+            onConfirm = { viewModel.setSpecialDatesTitleTemplate(type, it); editTemplate = null },
+            onDismiss = { editTemplate = null },
+        )
+    }
+}
+
+@Composable
+private fun SpecialDatesDisableDialog(
+    message: String,
+    onConfirm: () -> Unit,
+    onDismiss: () -> Unit,
+) {
+    androidx.compose.material3.AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text(stringResource(R.string.settings_special_dates_disable_title)) },
+        text = { Text(message) },
+        confirmButton = {
+            androidx.compose.material3.TextButton(onClick = onConfirm) {
+                Text(stringResource(R.string.settings_special_dates_disable_confirm))
+            }
+        },
+        dismissButton = {
+            androidx.compose.material3.TextButton(onClick = onDismiss) {
+                Text(stringResource(R.string.dialog_cancel))
+            }
+        },
+    )
+}
+
+@Composable
+private fun SpecialDatesTemplateDialog(
+    initial: String,
+    onConfirm: (String) -> Unit,
+    onDismiss: () -> Unit,
+) {
+    var text by rememberSaveable { mutableStateOf(initial) }
+    androidx.compose.material3.AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text(stringResource(R.string.settings_special_dates_template)) },
+        text = {
+            Column {
+                androidx.compose.material3.OutlinedTextField(
+                    value = text,
+                    onValueChange = { text = it },
+                    singleLine = true,
+                    modifier = Modifier.fillMaxWidth(),
+                )
+                Spacer(Modifier.height(8.dp))
+                Text(
+                    text = stringResource(R.string.settings_special_dates_template_hint),
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                )
+            }
+        },
+        confirmButton = {
+            androidx.compose.material3.TextButton(
+                onClick = { onConfirm(text) },
+                enabled = text.isNotBlank(),
+            ) { Text(stringResource(R.string.dialog_save)) }
+        },
+        dismissButton = {
+            androidx.compose.material3.TextButton(onClick = onDismiss) {
+                Text(stringResource(R.string.dialog_cancel))
+            }
+        },
+    )
+}
+
+private fun specialDateTypeLabel(type: SpecialDateType): Int = when (type) {
+    SpecialDateType.Birthday -> R.string.settings_special_dates_type_birthday
+    SpecialDateType.Anniversary -> R.string.settings_special_dates_type_anniversary
+    SpecialDateType.Custom -> R.string.settings_special_dates_type_custom
+}
+
+private fun hasContactsPermission(context: Context): Boolean =
+    ContextCompat.checkSelfPermission(context, Manifest.permission.READ_CONTACTS) ==
+        PackageManager.PERMISSION_GRANTED
+
+@Composable
+private fun specialDatesLastRunLabel(context: Context, lastRun: Long): String =
+    if (lastRun <= 0L) {
+        stringResource(R.string.settings_special_dates_never_synced)
+    } else {
+        stringResource(
+            R.string.settings_special_dates_last_synced,
+            android.text.format.DateUtils.getRelativeTimeSpanString(
+                lastRun,
+                System.currentTimeMillis(),
+                android.text.format.DateUtils.MINUTE_IN_MILLIS,
+            ).toString(),
+        )
+    }
+
 /** Which calendar + event kind a per-calendar reminder-override dialog targets. */
 private data class OverrideTarget(val calendarId: Long, val isAllDay: Boolean)
 

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsUiState.kt

@@ -7,6 +7,7 @@ import de.jeanlucmakiola.calendula.data.prefs.TimeFormatPref
 import de.jeanlucmakiola.calendula.data.prefs.WeekStartPref
 import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventFormField
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
 import de.jeanlucmakiola.calendula.ui.agenda.AgendaRange
 import de.jeanlucmakiola.calendula.ui.common.CalendarView
 
@@ -70,3 +71,20 @@ data class SettingsUiState(
      */
     val allowColorOnUnsupportedCalendars: Boolean = false,
 )
+
+/**
+ * State for the contact special-dates sub-page (issue #15). Exposed as its own
+ * flow rather than folded into [SettingsUiState] (whose combine is already full).
+ * [titleTemplates] is always populated — a blank stored template resolves to the
+ * localized default so the editor never shows an empty field.
+ */
+data class SpecialDatesUiState(
+    val enabled: Boolean = false,
+    val types: Set<SpecialDateType> = SpecialDateType.entries.toSet(),
+    val titleTemplates: Map<SpecialDateType, String> = emptyMap(),
+    val showAge: Boolean = true,
+    /** True when READ_CONTACTS was revoked after enabling — the mirror is paused. */
+    val stalledPermission: Boolean = false,
+    /** Epoch millis of the last sync, or 0 if it has never run. */
+    val lastRun: Long = 0L,
+)

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsViewModel.kt

@@ -10,14 +10,22 @@ import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
 import dagger.hilt.android.qualifiers.ApplicationContext
 import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
+import de.jeanlucmakiola.calendula.data.contacts.SpecialDatesCalendarSpec
+import de.jeanlucmakiola.calendula.data.contacts.SpecialDatesScheduler
+import de.jeanlucmakiola.calendula.data.contacts.SpecialDatesSyncEngine
+import de.jeanlucmakiola.calendula.data.di.IoDispatcher
 import de.jeanlucmakiola.calendula.data.prefs.CalendarReminderOverride
 import de.jeanlucmakiola.calendula.data.prefs.PastEventDisplay
 import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
+import de.jeanlucmakiola.calendula.data.prefs.SpecialDatesStalledReason
 import de.jeanlucmakiola.calendula.data.prefs.ThemeMode
 import de.jeanlucmakiola.calendula.data.prefs.TimeFormatPref
 import de.jeanlucmakiola.calendula.data.prefs.WeekStartPref
 import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventFormField
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.withContext
 import de.jeanlucmakiola.calendula.ui.agenda.AgendaRange
 import de.jeanlucmakiola.calendula.ui.agenda.storageValue
 import de.jeanlucmakiola.calendula.ui.common.CalendarView
@@ -41,6 +49,9 @@ import javax.inject.Inject
 class SettingsViewModel @Inject constructor(
     private val prefs: SettingsPrefs,
     repository: CalendarRepository,
+    private val specialDatesEngine: SpecialDatesSyncEngine,
+    specialDatesSpec: SpecialDatesCalendarSpec,
+    @IoDispatcher private val io: CoroutineDispatcher,
     @ApplicationContext private val appContext: Context,
 ) : ViewModel() {
 
@@ -166,6 +177,77 @@ class SettingsViewModel @Inject constructor(
         val dimCompletedEvents: Boolean,
     )
 
+    /** Contact special-dates sub-page (issue #15); its own flow — the main state is full. */
+    val specialDatesState: StateFlow<SpecialDatesUiState> = combine(
+        prefs.specialDatesEnabled,
+        prefs.specialDatesTypes,
+        prefs.specialDatesTitleTemplates,
+        prefs.specialDatesShowAge,
+        prefs.specialDatesStatus,
+    ) { enabled, types, templates, showAge, status ->
+        SpecialDatesUiState(
+            enabled = enabled,
+            types = types,
+            // A blank stored template resolves to the localized default so the
+            // editor always shows something sensible.
+            titleTemplates = SpecialDateType.entries.associateWith { type ->
+                templates[type]?.takeIf { it.isNotBlank() }
+                    ?: specialDatesSpec.defaultTitleTemplate(type)
+            },
+            showAge = showAge,
+            stalledPermission = status.stalled == SpecialDatesStalledReason.PermissionRevoked,
+            lastRun = status.lastRun,
+        )
+    }.stateIn(
+        scope = viewModelScope,
+        started = SharingStarted.WhileSubscribed(5_000L),
+        initialValue = SpecialDatesUiState(),
+    )
+
+    /**
+     * Turn the mirror on or off. Enabling schedules the daily job and runs an
+     * immediate sync (which creates the calendars); disabling cancels the job and
+     * tears the managed calendars down. The caller must have READ_CONTACTS granted
+     * before enabling.
+     */
+    fun setSpecialDatesEnabled(enabled: Boolean) {
+        viewModelScope.launch {
+            prefs.setSpecialDatesEnabled(enabled)
+            if (enabled) {
+                SpecialDatesScheduler.apply(appContext, enabled = true)
+                SpecialDatesScheduler.runNow(appContext)
+            } else {
+                SpecialDatesScheduler.apply(appContext, enabled = false)
+                withContext(io) { specialDatesEngine.teardown() }
+            }
+        }
+    }
+
+    fun setSpecialDateTypeEnabled(type: SpecialDateType, enabled: Boolean) {
+        viewModelScope.launch {
+            prefs.setSpecialDateTypeEnabled(type, enabled)
+            // Reconcile now: create the new type's calendar, or delete a disabled one.
+            SpecialDatesScheduler.runNow(appContext)
+        }
+    }
+
+    fun setSpecialDatesTitleTemplate(type: SpecialDateType, template: String) {
+        viewModelScope.launch {
+            prefs.setSpecialDatesTitleTemplate(type, template.trim())
+            SpecialDatesScheduler.runNow(appContext)
+        }
+    }
+
+    fun setSpecialDatesShowAge(enabled: Boolean) {
+        viewModelScope.launch {
+            prefs.setSpecialDatesShowAge(enabled)
+            SpecialDatesScheduler.runNow(appContext)
+        }
+    }
+
+    /** Kick off an immediate reconcile (the "Sync now" action). */
+    fun syncSpecialDatesNow() = SpecialDatesScheduler.runNow(appContext)
+
     fun setThemeMode(mode: ThemeMode) {
         viewModelScope.launch { prefs.setThemeMode(mode) }
     }

app/src/main/res/values-de/strings.xml

@@ -13,7 +13,7 @@
 
     <!-- Permission-Flow (F1) -->
     <string name="permission_rationale_title">Alle Termine, schön im Blick</string>
-    <string name="permission_rationale_body">Calendula braucht Zugriff auf deinen Kalender, um deine Termine zu zeigen und zu verwalten. Mehr verlangt die App nie.</string>
+    <string name="permission_rationale_body">Calendula braucht Zugriff auf deinen Kalender, um deine Termine zu zeigen und zu verwalten. Mehr verlangt die App zu Beginn nicht — und nichts verlässt je dein Gerät.</string>
     <string name="permission_request_button">Kalender-Zugriff erlauben</string>
     <string name="permission_denied_title">Kalender-Zugriff abgelehnt</string>
     <string name="permission_denied_body">Ohne Kalender-Zugriff kann Calendula keine Termine anzeigen. Du kannst den Zugriff in den System-Einstellungen wieder erlauben.</string>
@@ -410,4 +410,36 @@
     <string name="crash_report_open_failed">Der Issue-Tracker konnte nicht geöffnet werden. Der Bericht ist in deiner Zwischenablage.</string>
     <string name="crash_report_body_template">Danke, dass du einen Absturz in Calendula meldest. Bitte ergänze, was du gerade getan hast, und sende dann ab.\n\n### Was ist passiert\n\n\n### Absturzbericht\n%1$s\n</string>
     <string name="crash_report_body_paste">_(Der Bericht war zu lang für diesen Link — füge ihn aus deiner Zwischenablage hier ein.)_</string>
+
+    <!-- Contact special dates (issue #15) -->
+    <string name="special_dates_calendar_birthday">Geburtstage</string>
+    <string name="special_dates_calendar_anniversary">Jahrestage</string>
+    <string name="special_dates_calendar_custom">Besondere Tage</string>
+    <string name="special_dates_default_title_birthday">{name}s Geburtstag ({age})</string>
+    <string name="special_dates_default_title_anniversary">{name}s Jahrestag ({age})</string>
+    <string name="special_dates_default_title_custom">{name}</string>
+    <string name="event_edit_managed_hint">Verwaltet von „%1$s“ — Titel, Datum und Wiederholung werden aus deinen Kontakten synchron gehalten. Erinnerungen, Ort und Notizen kannst du selbst bearbeiten.</string>
+    <string name="settings_special_dates_subtitle">Geburtstage &amp; Jahrestage aus Kontakten</string>
+    <string name="settings_section_special_dates">Besondere Kontakttage</string>
+    <string name="settings_special_dates_enable">Kontakttage anzeigen</string>
+    <string name="settings_special_dates_enable_hint">Spiegelt Geburtstage und weitere Daten deiner Kontakte in lokale Kalender. Liest Kontakte nur auf diesem Gerät — nichts wird hochgeladen, und deine Kontakte werden nie verändert.</string>
+    <string name="settings_special_dates_type_birthday">Geburtstage</string>
+    <string name="settings_special_dates_type_anniversary">Jahrestage</string>
+    <string name="settings_special_dates_type_custom">Weitere Tage</string>
+    <string name="settings_special_dates_template">Titelformat</string>
+    <string name="settings_special_dates_template_hint">Verwende {name} für den Kontakt und {age} für das Alter (ausgeblendet, wenn das Jahr unbekannt ist).</string>
+    <string name="settings_special_dates_show_age">Alter anzeigen</string>
+    <string name="settings_special_dates_show_age_hint">{age} in Titeln anzeigen, wenn das Geburtsjahr bekannt ist</string>
+    <string name="settings_special_dates_sync_now">Jetzt synchronisieren</string>
+    <string name="settings_special_dates_never_synced">Noch nicht synchronisiert</string>
+    <string name="settings_special_dates_last_synced">Zuletzt synchronisiert %1$s</string>
+    <string name="settings_special_dates_calendar_hint">Farbe, Sichtbarkeit und Erinnerungen jedes Kalenders legst du in den Kalender-Einstellungen fest.</string>
+    <string name="settings_special_dates_paused_title">Pausiert</string>
+    <string name="settings_special_dates_paused_hint">Calendula kann deine Kontakte nicht mehr lesen, daher werden diese Kalender nicht aktualisiert.</string>
+    <string name="settings_special_dates_grant">Zugriff erlauben</string>
+    <string name="settings_special_dates_disable_title">Kontakttage deaktivieren?</string>
+    <string name="settings_special_dates_disable_all_message">Dadurch werden die Kontakttage-Kalender und ihre Termine gelöscht. Hinzugefügte Erinnerungen oder Notizen gehen verloren.</string>
+    <string name="settings_special_dates_disable_type_message">Dadurch werden der Kalender „%1$s“ und seine Termine gelöscht. Hinzugefügte Erinnerungen oder Notizen gehen verloren.</string>
+    <string name="settings_special_dates_disable_confirm">Deaktivieren</string>
+    <string name="dialog_save">Speichern</string>
 </resources>

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

@@ -14,7 +14,7 @@
 
     <!-- Permission flow (F1) -->
     <string name="permission_rationale_title">See all your events, beautifully</string>
-    <string name="permission_rationale_body">Calendula needs access to your calendar to show and manage your events. That\'s the only thing it ever asks for.</string>
+    <string name="permission_rationale_body">Calendula needs access to your calendar to show and manage your events. That\'s all it asks for up front — and nothing ever leaves your device.</string>
     <string name="permission_request_button">Grant calendar access</string>
     <string name="permission_denied_title">Calendar access denied</string>
     <string name="permission_denied_body">Calendula cannot show events without calendar access. You can grant it again in the system settings.</string>
@@ -68,6 +68,8 @@
     <string name="event_edit_close">Close</string>
     <string name="event_edit_save">Save</string>
     <string name="event_edit_title_hint">Add title</string>
+    <!-- %1$s is the managing calendar's name, e.g. "Birthdays". -->
+    <string name="event_edit_managed_hint">Managed by “%1$s” — the title, date and repeat are kept in sync from your contacts. Reminders, location and notes are yours to edit.</string>
     <string name="event_edit_starts">Starts</string>
     <string name="event_edit_ends">Ends</string>
     <string name="event_edit_error_end_before_start">Ends before it starts</string>
@@ -344,6 +346,33 @@
     <string name="settings_appearance_subtitle">Theme, default view, week start</string>
     <string name="settings_event_form_subtitle">Default fields for new events</string>
     <string name="settings_notifications_subtitle">Event reminders</string>
+    <string name="settings_special_dates_subtitle">Contact birthdays &amp; anniversaries</string>
+
+    <!-- Contact special dates (issue #15) -->
+    <string name="settings_section_special_dates">Contact special dates</string>
+    <string name="settings_special_dates_enable">Show contact dates</string>
+    <string name="settings_special_dates_enable_hint">Mirror your contacts\' birthdays and other dates into local calendars. Reads contacts on this device only — nothing is uploaded, and your contacts are never changed.</string>
+    <string name="settings_special_dates_type_birthday">Birthdays</string>
+    <string name="settings_special_dates_type_anniversary">Anniversaries</string>
+    <string name="settings_special_dates_type_custom">Other dates</string>
+    <string name="settings_special_dates_template">Title format</string>
+    <string name="settings_special_dates_template_hint">Use {name} for the contact and {age} for their age (hidden when the year is unknown).</string>
+    <string name="settings_special_dates_show_age">Show age</string>
+    <string name="settings_special_dates_show_age_hint">Include {age} in titles when the birth year is known</string>
+    <string name="settings_special_dates_sync_now">Sync now</string>
+    <string name="settings_special_dates_never_synced">Not synced yet</string>
+    <!-- %1$s is a relative time, e.g. "5 minutes ago". -->
+    <string name="settings_special_dates_last_synced">Last synced %1$s</string>
+    <string name="settings_special_dates_calendar_hint">Set each calendar\'s colour, visibility and reminders in Calendars settings.</string>
+    <string name="settings_special_dates_paused_title">Paused</string>
+    <string name="settings_special_dates_paused_hint">Calendula can no longer read your contacts, so these calendars aren\'t updating.</string>
+    <string name="settings_special_dates_grant">Grant access</string>
+    <string name="settings_special_dates_disable_title">Turn off contact dates?</string>
+    <string name="settings_special_dates_disable_all_message">This deletes the contact-date calendars and their events. Any reminders or notes you added to them will be lost.</string>
+    <!-- %1$s is the date type, e.g. "Birthdays". -->
+    <string name="settings_special_dates_disable_type_message">This deletes the “%1$s” calendar and its events. Any reminders or notes you added to them will be lost.</string>
+    <string name="settings_special_dates_disable_confirm">Turn off</string>
+    <string name="dialog_save">Save</string>
     <string name="settings_section_about">About</string>
     <string name="settings_license">License</string>
     <string name="settings_license_value">MIT</string>
@@ -462,4 +491,13 @@
     <string name="crash_report_body_paste">_(The report was too long for this link — paste it from your clipboard here.)_</string>
     <string name="report_issue_url" translatable="false">https://codeberg.org/jlmakiola/calendula/issues/new</string>
     <string name="report_issue_choose_url" translatable="false">https://codeberg.org/jlmakiola/calendula/issues/new/choose</string>
+
+    <!-- Contact special dates (issue #15). {name} is the contact, {age} the age
+         at the upcoming date (dropped when the year is unknown or Show age is off). -->
+    <string name="special_dates_calendar_birthday">Birthdays</string>
+    <string name="special_dates_calendar_anniversary">Anniversaries</string>
+    <string name="special_dates_calendar_custom">Special dates</string>
+    <string name="special_dates_default_title_birthday">{name}\'s birthday ({age})</string>
+    <string name="special_dates_default_title_anniversary">{name}\'s anniversary ({age})</string>
+    <string name="special_dates_default_title_custom">{name}</string>
 </resources>

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/FakeCalendarDataSource.kt

@@ -1,12 +1,15 @@
 package de.jeanlucmakiola.calendula.data.calendar
 
+import android.provider.CalendarContract
 import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventColorOption
 import de.jeanlucmakiola.calendula.domain.EventDetail
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
 import de.jeanlucmakiola.calendula.domain.ics.IcsEvent
 import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
+import java.time.ZoneId
 
 /**
  * Test-only fake. Tunable via the three `var` properties; `tick()` simulates
@@ -83,6 +86,8 @@ internal class FakeCalendarDataSource : CalendarDataSource {
     override fun deleteCalendar(id: Long) {
         writeError?.let { throw it }
         deletedCalendarIds += id
+        managedCalendarRows.removeAll { it.id == id }
+        managedEvents.remove(id)
     }
 
     /** All-day reminder fire-time minute-of-day passed into the last write. */
@@ -139,6 +144,68 @@ internal class FakeCalendarDataSource : CalendarDataSource {
     override fun deleteEvent(eventId: Long) {
         writeError?.let { throw it }
         deletedEventIds += eventId
+        managedEvents.values.forEach { rows -> rows.removeAll { it.eventId == eventId } }
+    }
+
+    // --- Managed special-dates surface (stateful, so a re-sync sees inserts) ---
+
+    var nextManagedEventId: Long = 1_000L
+    private var managedCalendarSeq: Long = 700L
+    private val managedCalendarRows = mutableListOf<ManagedCalendarRow>()
+    private val managedEvents = mutableMapOf<Long, MutableList<ManagedEventRow>>()
+
+    data class CreatedManagedCalendar(val displayName: String, val color: Int, val type: SpecialDateType)
+    val createdManagedCalendars = mutableListOf<CreatedManagedCalendar>()
+    val insertedManagedEvents = mutableListOf<Pair<EventForm, String>>()
+    val updatedManagedFields = mutableListOf<Pair<Long, Map<String, Any?>>>()
+
+    /** Preset an orphan managed calendar (e.g. to test adoption after a prefs wipe). */
+    fun presetManagedCalendar(id: Long, type: SpecialDateType) {
+        managedCalendarRows += ManagedCalendarRow(id, type)
+        managedEvents.getOrPut(id) { mutableListOf() }
+    }
+
+    override fun createManagedCalendar(displayName: String, color: Int, type: SpecialDateType): Long {
+        writeError?.let { throw it }
+        createdManagedCalendars += CreatedManagedCalendar(displayName, color, type)
+        val id = managedCalendarSeq++
+        managedCalendarRows += ManagedCalendarRow(id, type)
+        managedEvents.getOrPut(id) { mutableListOf() }
+        return id
+    }
+
+    override fun findManagedCalendars(): List<ManagedCalendarRow> = managedCalendarRows.toList()
+
+    override fun queryManagedEvents(calendarId: Long): List<ManagedEventRow> =
+        managedEvents[calendarId]?.toList() ?: emptyList()
+
+    override fun insertManagedEvent(form: EventForm, uid: String, allDayReminderTimeMinutes: Int): Long {
+        writeError?.let { throw it }
+        insertedManagedEvents += form to uid
+        allDayReminderTimes += allDayReminderTimeMinutes
+        val id = nextManagedEventId++
+        val times = form.toWriteTimes(ZoneId.systemDefault())
+        managedEvents.getOrPut(requireNotNull(form.calendarId)) { mutableListOf() } +=
+            ManagedEventRow(id, uid, form.title.trim(), times.dtStartMillis, form.rrule)
+        return id
+    }
+
+    override fun updateManagedFields(eventId: Long, values: Map<String, Any?>) {
+        writeError?.let { throw it }
+        if (values.isEmpty()) return
+        updatedManagedFields += eventId to values
+        managedEvents.values.forEach { rows ->
+            val idx = rows.indexOfFirst { it.eventId == eventId }
+            if (idx >= 0) {
+                var row = rows[idx]
+                (values[CalendarContract.Events.TITLE] as? String)?.let { row = row.copy(title = it) }
+                (values[CalendarContract.Events.DTSTART] as? Long)?.let { row = row.copy(dtStartMillis = it) }
+                if (values.containsKey(CalendarContract.Events.RRULE)) {
+                    row = row.copy(rrule = values[CalendarContract.Events.RRULE] as? String)
+                }
+                rows[idx] = row
+            }
+        }
     }
 
     override fun deleteOccurrence(eventId: Long, beginMillis: Long) {

app/src/test/java/de/jeanlucmakiola/calendula/data/contacts/SpecialDatesSyncEngineTest.kt

@@ -0,0 +1,196 @@
+package de.jeanlucmakiola.calendula.data.contacts
+
+import android.provider.CalendarContract
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.PreferenceDataStoreFactory
+import androidx.datastore.preferences.core.Preferences
+import com.google.common.truth.Truth.assertThat
+import de.jeanlucmakiola.calendula.data.calendar.FakeCalendarDataSource
+import de.jeanlucmakiola.calendula.data.calendar.ManagedEventRow
+import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
+import de.jeanlucmakiola.calendula.domain.contacts.ContactSpecialDate
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.runTest
+import kotlinx.datetime.LocalDate
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.io.TempDir
+import java.nio.file.Path
+
+class SpecialDatesSyncEngineTest {
+
+    private val today = LocalDate(2026, 3, 1)
+
+    private class FakeContacts(
+        var permission: Boolean = true,
+        var dates: List<ContactSpecialDate> = emptyList(),
+    ) : ContactSpecialDatesDataSource {
+        override fun hasPermission() = permission
+        override fun readSpecialDates() = dates
+    }
+
+    private class FakeSpec : SpecialDatesCalendarSpec {
+        override fun displayName(type: SpecialDateType) = type.name
+        override fun color(type: SpecialDateType) = 0xFF112233.toInt()
+        override fun defaultTitleTemplate(type: SpecialDateType) = when (type) {
+            SpecialDateType.Birthday -> "{name}'s birthday ({age})"
+            SpecialDateType.Anniversary -> "{name}'s anniversary"
+            SpecialDateType.Custom -> "{name}"
+        }
+    }
+
+    private fun prefs(tempDir: Path): SettingsPrefs {
+        val store: DataStore<Preferences> = PreferenceDataStoreFactory.create(
+            produceFile = { tempDir.resolve("settings_test.preferences_pb").toFile() },
+        )
+        return SettingsPrefs(store)
+    }
+
+    private fun birthday(key: String, name: String, month: Int, day: Int, year: Int?) =
+        ContactSpecialDate(key, name, SpecialDateType.Birthday, month, day, year)
+
+    private suspend fun engineWith(
+        tempDir: Path,
+        contacts: FakeContacts,
+        calendars: FakeCalendarDataSource = FakeCalendarDataSource(),
+        enabled: Boolean = true,
+    ): Pair<SpecialDatesSyncEngine, SettingsPrefs> {
+        val settings = prefs(tempDir)
+        if (enabled) settings.setSpecialDatesEnabled(true)
+        return SpecialDatesSyncEngine(contacts, calendars, settings, FakeSpec()) to settings
+    }
+
+    @Test
+    fun `disabled feature is a no-op`(@TempDir tempDir: Path) = runTest {
+        val calendars = FakeCalendarDataSource()
+        val (engine, _) = engineWith(tempDir, FakeContacts(), calendars, enabled = false)
+        assertThat(engine.sync(today)).isEqualTo(SpecialDatesSyncResult.Disabled)
+        assertThat(calendars.createdManagedCalendars).isEmpty()
+    }
+
+    @Test
+    fun `missing permission reports stalled without touching calendars`(@TempDir tempDir: Path) = runTest {
+        val calendars = FakeCalendarDataSource()
+        val (engine, _) = engineWith(tempDir, FakeContacts(permission = false), calendars)
+        assertThat(engine.sync(today)).isEqualTo(SpecialDatesSyncResult.PermissionMissing)
+        assertThat(calendars.createdManagedCalendars).isEmpty()
+    }
+
+    @Test
+    fun `first sync creates calendars and inserts one event per contact`(@TempDir tempDir: Path) = runTest {
+        val calendars = FakeCalendarDataSource()
+        val contacts = FakeContacts(
+            dates = listOf(
+                birthday("a", "Jane", 5, 14, 1990),
+                birthday("b", "Bob", 12, 25, null),
+            ),
+        )
+        val (engine, settings) = engineWith(tempDir, contacts, calendars)
+
+        assertThat(engine.sync(today)).isEqualTo(SpecialDatesSyncResult.Success)
+        // All three type calendars exist; the birthday one holds both contacts.
+        assertThat(calendars.createdManagedCalendars.map { it.type })
+            .containsExactlyElementsIn(SpecialDateType.entries)
+        assertThat(calendars.insertedManagedEvents).hasSize(2)
+        assertThat(calendars.insertedManagedEvents.map { it.second })
+            .containsExactly("contact-birthday:a@calendula", "contact-birthday:b@calendula")
+        // Year-less contact drops the age; year-known keeps it.
+        val titles = calendars.insertedManagedEvents.map { it.first.title }
+        assertThat(titles).contains("Jane's birthday (36)")
+        assertThat(titles).contains("Bob's birthday")
+        // Calendar ids were persisted for the editor / next sync.
+        assertThat(settings.specialDatesCalendars.first()).containsKey(SpecialDateType.Birthday)
+    }
+
+    @Test
+    fun `a second sync with no changes writes nothing`(@TempDir tempDir: Path) = runTest {
+        val calendars = FakeCalendarDataSource()
+        val contacts = FakeContacts(dates = listOf(birthday("a", "Jane", 5, 14, 1990)))
+        val (engine, _) = engineWith(tempDir, contacts, calendars)
+
+        engine.sync(today)
+        val insertsAfterFirst = calendars.insertedManagedEvents.size
+        val calendarsAfterFirst = calendars.createdManagedCalendars.size
+        engine.sync(today)
+
+        assertThat(calendars.insertedManagedEvents).hasSize(insertsAfterFirst)
+        assertThat(calendars.createdManagedCalendars).hasSize(calendarsAfterFirst)
+        assertThat(calendars.updatedManagedFields).isEmpty()
+        assertThat(calendars.deletedEventIds).isEmpty()
+    }
+
+    @Test
+    fun `a renamed contact triggers a title-only managed update`(@TempDir tempDir: Path) = runTest {
+        val calendars = FakeCalendarDataSource()
+        val contacts = FakeContacts(dates = listOf(birthday("a", "Jane", 5, 14, 1990)))
+        val (engine, _) = engineWith(tempDir, contacts, calendars)
+        engine.sync(today)
+
+        contacts.dates = listOf(birthday("a", "Janet", 5, 14, 1990))
+        engine.sync(today)
+
+        assertThat(calendars.updatedManagedFields).hasSize(1)
+        val (_, columns) = calendars.updatedManagedFields.single()
+        // Only managed columns are ever written — never reminders/location.
+        assertThat(columns.keys).containsExactly(CalendarContract.Events.TITLE)
+        assertThat(columns[CalendarContract.Events.TITLE]).isEqualTo("Janet's birthday (36)")
+    }
+
+    @Test
+    fun `a removed contact deletes its event`(@TempDir tempDir: Path) = runTest {
+        val calendars = FakeCalendarDataSource()
+        val contacts = FakeContacts(dates = listOf(birthday("a", "Jane", 5, 14, 1990)))
+        val (engine, _) = engineWith(tempDir, contacts, calendars)
+        engine.sync(today)
+
+        contacts.dates = emptyList()
+        engine.sync(today)
+
+        assertThat(calendars.deletedEventIds).hasSize(1)
+    }
+
+    @Test
+    fun `disabling a type deletes its calendar on the next sync`(@TempDir tempDir: Path) = runTest {
+        val calendars = FakeCalendarDataSource()
+        val (engine, settings) = engineWith(tempDir, FakeContacts(), calendars)
+        engine.sync(today)
+        val anniversaryId = settings.specialDatesCalendars.first().getValue(SpecialDateType.Anniversary)
+
+        settings.setSpecialDateTypeEnabled(SpecialDateType.Anniversary, false)
+        engine.sync(today)
+
+        assertThat(calendars.deletedCalendarIds).contains(anniversaryId)
+        assertThat(settings.specialDatesCalendars.first()).doesNotContainKey(SpecialDateType.Anniversary)
+    }
+
+    // --- pure diff ---
+
+    private fun desired(uid: String, title: String, dt: Long, rrule: String? = "FREQ=YEARLY") =
+        ManagedEventDesired(uid, title, dt, rrule)
+
+    private fun row(id: Long, uid: String, title: String, dt: Long, rrule: String? = "FREQ=YEARLY") =
+        ManagedEventRow(id, uid, title, dt, rrule)
+
+    @Test
+    fun `diff inserts new, deletes gone, and leaves unchanged alone`() {
+        val diff = diffManagedEvents(
+            desired = listOf(desired("keep", "Jane", 100), desired("new", "Ada", 200)),
+            existing = listOf(row(1, "keep", "Jane", 100), row(2, "gone", "Old", 300)),
+        )
+        assertThat(diff.insertUids).containsExactly("new")
+        assertThat(diff.deleteEventIds).containsExactly(2L)
+        assertThat(diff.updates).isEmpty()
+    }
+
+    @Test
+    fun `diff emits only the changed managed columns`() {
+        val diff = diffManagedEvents(
+            desired = listOf(desired("a", "Janet", 150)),
+            existing = listOf(row(9, "a", "Jane", 100)),
+        )
+        val update = diff.updates.single()
+        assertThat(update.eventId).isEqualTo(9L)
+        assertThat(update.columns.keys)
+            .containsExactly(CalendarContract.Events.TITLE, CalendarContract.Events.DTSTART)
+    }
+}

app/src/test/java/de/jeanlucmakiola/calendula/data/prefs/SettingsPrefsTest.kt

@@ -5,6 +5,7 @@ import androidx.datastore.preferences.core.PreferenceDataStoreFactory
 import androidx.datastore.preferences.core.Preferences
 import com.google.common.truth.Truth.assertThat
 import de.jeanlucmakiola.calendula.domain.EventFormField
+import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
 import de.jeanlucmakiola.calendula.ui.agenda.AgendaRange
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.test.runTest
@@ -340,4 +341,59 @@ class SettingsPrefsTest {
         assertThat(WeekStartPref.Auto.resolveFirstDay(Locale.GERMANY)).isEqualTo(DayOfWeek.MONDAY)
         assertThat(WeekStartPref.Auto.resolveFirstDay(Locale.US)).isEqualTo(DayOfWeek.SUNDAY)
     }
+
+    @Test
+    fun `special dates feature is off with all types on by default`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        assertThat(prefs.specialDatesEnabled.first()).isFalse()
+        assertThat(prefs.specialDatesTypes.first()).isEqualTo(SpecialDateType.entries.toSet())
+        assertThat(prefs.specialDatesCalendars.first()).isEmpty()
+        assertThat(prefs.managedCalendarIds.first()).isEmpty()
+        assertThat(prefs.specialDatesShowAge.first()).isTrue()
+    }
+
+    @Test
+    fun `special date type toggles round-trip`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        prefs.setSpecialDateTypeEnabled(SpecialDateType.Anniversary, false)
+        assertThat(prefs.specialDatesTypes.first())
+            .isEqualTo(setOf(SpecialDateType.Birthday, SpecialDateType.Custom))
+    }
+
+    @Test
+    fun `managed calendar ids round-trip and drive managedCalendarIds`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        prefs.setSpecialDatesCalendarId(SpecialDateType.Birthday, 7L)
+        prefs.setSpecialDatesCalendarId(SpecialDateType.Anniversary, 9L)
+        assertThat(prefs.specialDatesCalendars.first())
+            .isEqualTo(mapOf(SpecialDateType.Birthday to 7L, SpecialDateType.Anniversary to 9L))
+        assertThat(prefs.managedCalendarIds.first()).isEqualTo(setOf(7L, 9L))
+
+        prefs.setSpecialDatesCalendarId(SpecialDateType.Birthday, null)
+        assertThat(prefs.specialDatesCalendars.first())
+            .isEqualTo(mapOf(SpecialDateType.Anniversary to 9L))
+    }
+
+    @Test
+    fun `title template round-trips per type`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        assertThat(prefs.specialDatesTitleTemplates.first()[SpecialDateType.Birthday]).isEmpty()
+        prefs.setSpecialDatesTitleTemplate(SpecialDateType.Birthday, "{name}'s birthday")
+        assertThat(prefs.specialDatesTitleTemplates.first()[SpecialDateType.Birthday])
+            .isEqualTo("{name}'s birthday")
+    }
+
+    @Test
+    fun `sync status records run and stalled reason`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        assertThat(prefs.specialDatesStatus.first())
+            .isEqualTo(SpecialDatesStatus(lastRun = 0L, stalled = null))
+
+        prefs.recordSpecialDatesRun(1000L, SpecialDatesStalledReason.PermissionRevoked)
+        assertThat(prefs.specialDatesStatus.first())
+            .isEqualTo(SpecialDatesStatus(1000L, SpecialDatesStalledReason.PermissionRevoked))
+
+        prefs.recordSpecialDatesRun(2000L, null)
+        assertThat(prefs.specialDatesStatus.first()).isEqualTo(SpecialDatesStatus(2000L, null))
+    }
 }

app/src/test/java/de/jeanlucmakiola/calendula/domain/contacts/ContactSpecialDateTest.kt

@@ -0,0 +1,64 @@
+package de.jeanlucmakiola.calendula.domain.contacts
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.Test
+
+class ContactSpecialDateTest {
+
+    @Test
+    fun `parses a full yyyy-MM-dd date with year`() {
+        val parts = parseContactEventDate("1990-05-14")
+        assertThat(parts).isEqualTo(ContactDateParts(year = 1990, month = 5, day = 14))
+    }
+
+    @Test
+    fun `parses a year-less --MM-dd date`() {
+        val parts = parseContactEventDate("--05-14")
+        assertThat(parts).isEqualTo(ContactDateParts(year = null, month = 5, day = 14))
+    }
+
+    @Test
+    fun `parses a compact yyyyMMdd date`() {
+        val parts = parseContactEventDate("19900514")
+        assertThat(parts).isEqualTo(ContactDateParts(year = 1990, month = 5, day = 14))
+    }
+
+    @Test
+    fun `parses a year-less MM-dd date without the double-dash prefix`() {
+        val parts = parseContactEventDate("12-25")
+        assertThat(parts).isEqualTo(ContactDateParts(year = null, month = 12, day = 25))
+    }
+
+    @Test
+    fun `keeps a year-less Feb 29 by validating against a leap anchor`() {
+        val parts = parseContactEventDate("--02-29")
+        assertThat(parts).isEqualTo(ContactDateParts(year = null, month = 2, day = 29))
+    }
+
+    @Test
+    fun `keeps Feb 29 in a real leap year`() {
+        assertThat(parseContactEventDate("2000-02-29"))
+            .isEqualTo(ContactDateParts(year = 2000, month = 2, day = 29))
+    }
+
+    @Test
+    fun `rejects Feb 29 in a non-leap year`() {
+        assertThat(parseContactEventDate("1999-02-29")).isNull()
+    }
+
+    @Test
+    fun `rejects an impossible month or day`() {
+        assertThat(parseContactEventDate("2020-13-01")).isNull()
+        assertThat(parseContactEventDate("2020-06-31")).isNull()
+        assertThat(parseContactEventDate("--00-10")).isNull()
+    }
+
+    @Test
+    fun `rejects blank, null and garbage input`() {
+        assertThat(parseContactEventDate(null)).isNull()
+        assertThat(parseContactEventDate("")).isNull()
+        assertThat(parseContactEventDate("   ")).isNull()
+        assertThat(parseContactEventDate("not-a-date")).isNull()
+        assertThat(parseContactEventDate("2020")).isNull()
+    }
+}

app/src/test/java/de/jeanlucmakiola/calendula/domain/contacts/SpecialDateFormattingTest.kt

@@ -0,0 +1,69 @@
+package de.jeanlucmakiola.calendula.domain.contacts
+
+import com.google.common.truth.Truth.assertThat
+import kotlinx.datetime.LocalDate
+import org.junit.jupiter.api.Test
+
+class SpecialDateFormattingTest {
+
+    private fun birthday(month: Int, day: Int, year: Int?) = ContactSpecialDate(
+        lookupKey = "k",
+        displayName = "Jane",
+        type = SpecialDateType.Birthday,
+        month = month,
+        day = day,
+        year = year,
+    )
+
+    @Test
+    fun `uid is deterministic and namespaced by type`() {
+        assertThat(managedEventUid(SpecialDateType.Birthday, "abc"))
+            .isEqualTo("contact-birthday:abc@calendula")
+        assertThat(managedEventUid(SpecialDateType.Anniversary, "abc"))
+            .isEqualTo("contact-anniversary:abc@calendula")
+    }
+
+    @Test
+    fun `anchor date uses the known year`() {
+        assertThat(birthday(5, 14, 1990).anchorDate()).isEqualTo(LocalDate(1990, 5, 14))
+    }
+
+    @Test
+    fun `anchor date falls back to a leap year when year-less`() {
+        assertThat(birthday(2, 29, null).anchorDate()).isEqualTo(LocalDate(YEARLESS_ANCHOR_YEAR, 2, 29))
+    }
+
+    @Test
+    fun `age is null when the year is unknown`() {
+        assertThat(birthday(5, 14, null).ageAtNextOccurrence(LocalDate(2026, 1, 1))).isNull()
+    }
+
+    @Test
+    fun `age counts the upcoming birthday when it is still ahead this year`() {
+        // Born 1990-05-14; today 2026-03-01 → next birthday 2026 → turns 36.
+        assertThat(birthday(5, 14, 1990).ageAtNextOccurrence(LocalDate(2026, 3, 1))).isEqualTo(36)
+    }
+
+    @Test
+    fun `age rolls to next year once the birthday has passed`() {
+        // Born 1990-05-14; today 2026-06-01 → next birthday 2027 → turns 37.
+        assertThat(birthday(5, 14, 1990).ageAtNextOccurrence(LocalDate(2026, 6, 1))).isEqualTo(37)
+    }
+
+    @Test
+    fun `age counts today's birthday as this year`() {
+        assertThat(birthday(5, 14, 1990).ageAtNextOccurrence(LocalDate(2026, 5, 14))).isEqualTo(36)
+    }
+
+    @Test
+    fun `title substitutes name and age`() {
+        assertThat(renderSpecialDateTitle("{name}'s birthday ({age})", "Jane", 30))
+            .isEqualTo("Jane's birthday (30)")
+    }
+
+    @Test
+    fun `title drops an empty age parenthesis and tidies spacing`() {
+        assertThat(renderSpecialDateTitle("{name}'s birthday ({age})", "Jane", null))
+            .isEqualTo("Jane's birthday")
+    }
+}

docs/design/contact-special-dates.md

@@ -0,0 +1,246 @@
+# Design: Contact special-dates calendars (+ per-calendar multiple reminders)
+
+Status: **implemented** on `feat/contact-special-dates` (#14 prerequisite merged in)
+Date: 2026-06-30 (implemented 2026-07-01)
+Tracking: Codeberg #15 (feature), Codeberg #14 (prerequisite)
+
+Implementation notes / deviations from this design:
+
+- **Event identity key is a deterministic `Events.UID_2445`**
+  (`contact-<type>:<lookupKey>@calendula`), not `SYNC_DATA1`. On a LOCAL calendar
+  the provider drops `_sync` columns unless written through a sync-adapter URI;
+  `UID_2445` is written/read through the normal event URIs the app already uses
+  (and doubles as a stable iCal UID). The managed **calendar** still carries a
+  `CAL_SYNC2` marker for re-adoption (calendar-row writes already use the
+  sync-adapter URI).
+- **Age is a sync-time snapshot.** A `FREQ=YEARLY` row has one static title, so
+  `{age}` reflects the upcoming birthday at the last sync (refreshed daily / on
+  foreground), not a per-occurrence value.
+- New managed calendars seed a per-calendar all-day reminder default of
+  on-the-day + one week before, so birthdays get lead time out of the box.
+- Title template is user-editable from day one (`{name}`, `{age}`).
+
+This document captures the full design for surfacing contact birthdays —
+and, by extension, anniversaries and custom dates — as auto-updating local
+calendars in Calendula. It also specifies #14 (per-calendar *multiple*
+default reminders), which is a hard prerequisite and ships first.
+
+The two pieces are deliberately split across **two branches / two
+shipments**:
+
+- `feat/per-calendar-multi-reminders` — #14, ships first.
+- `feat/contact-special-dates` — #15, builds on #14.
+
+They *may* release together depending on timing, but #14 is independently
+useful and is the foundation the special-dates calendars lean on.
+
+---
+
+## Why this is worth doing carefully
+
+Calendula's identity is privacy: **no INTERNET permission**, and historically
+**no `READ_CONTACTS`** — guest-picking uses a one-shot `ACTION_PICK` so the app
+never holds the contacts permission (`EventEditScreen.kt:446-460`).
+
+This feature **declares `READ_CONTACTS`** for the first time. That is a
+deliberate, owner-approved shift, mitigated by:
+
+- The permission is **opt-in and feature-gated** — requested only when the user
+  enables the feature, never at startup.
+- Everything stays **offline**. Contacts are read locally and mirrored into a
+  local calendar; nothing leaves the device.
+- The mirror is **one-way** (contacts → calendar). Calendula never writes to
+  Contacts.
+
+Store listing / About copy will need to explain the optional permission.
+
+---
+
+## Prerequisite — #14: per-calendar *multiple* default reminders
+
+### Today
+
+- Events already support **multiple reminders** — `EventForm.reminders:
+  List<Int>` (`EventForm.kt:24`), each written as a separate
+  `CalendarContract.Reminders` row (`CalendarDataSource.kt:620-630`), each
+  firing independently. The runtime/notification path is done.
+- The **defaults** layer is single-valued, though:
+  - Global: `defaultReminderMinutes` / `defaultAllDayReminderMinutes` — single
+    `Int` (`SettingsPrefs.kt:287,302`).
+  - Per-calendar override: `perCalendarReminderOverride: Map<Long, Int?>` and
+    the all-day variant (`SettingsPrefs.kt:350-381`), resolved by
+    `resolveDefaultReminder()` (`SettingsPrefs.kt:509-524`).
+  - UI: expandable per-calendar override section
+    (`SettingsScreen.kt:879-953`); `ReminderDefaultPicker` (`:956+`).
+
+### The change
+
+Widen the **defaults**, not the runtime, from one reminder to a list:
+
+1. Resolution model `Int` → `List<Int>` in global defaults + per-calendar
+   override + `resolveDefaultReminder()`. The DataStore string format already
+   parses `id=value;id=value` (`SettingsPrefs.kt:576-577`); `value` becomes a
+   comma-separated list. Keep the `Inherit / None / Minutes` override states
+   (`CalendarReminderOverride`, `SettingsPrefs.kt:493-500`) — `Minutes` carries
+   a list.
+2. `ReminderDefaultPicker` → multi-select. Mirror the event-form multi-reminder
+   UI rather than inventing new interaction.
+3. New events seed `EventForm.reminders` from the **resolved list** instead of
+   a single value.
+
+No new permissions, no provider changes, no scheduling changes. Type widening
+plus one picker upgrade.
+
+### Why it gates #15
+
+Each special-dates calendar is a normal local calendar, so it inherits the
+**per-calendar reminder default** for free. A birthdays calendar is useless
+without lead time (the reporter literally asked for "a week before *and* on the
+day") — that requires *multiple* defaults, i.e. #14.
+
+---
+
+## #15: Contact special-dates calendars
+
+### Core model: one-way mirror, one local calendar per type
+
+Contacts → **separate local calendars per type**:
+
+- "Birthdays"
+- "Anniversaries"
+- "Custom dates" (everything else / `TYPE_OTHER` / `TYPE_CUSTOM`)
+
+Separate-per-type is the key architectural decision: each is a normal local
+calendar (`createLocalCalendar()`, `CalendarDataSource.kt:238-260`), so the
+**existing per-calendar infra applies for free**:
+
+- **Color** → existing per-calendar color.
+- **Show/hide** → existing calendar visibility.
+- **Default reminders** → per-calendar override from #14.
+
+This shrinks the new surface dramatically: anniversaries and custom dates are
+near copy-paste of birthdays (same engine, different `ContactsContract` data
+kind, one extra local calendar each), and the settings sub-page does **not**
+need to reinvent color/visibility/reminders.
+
+### Events: field-level managed, not read-only
+
+Calendula manages a few fields; the user owns the rest.
+
+- **Managed** (overwritten on every sync, disabled in the editor for these
+  events): title, start date, recurrence (`FREQ=YEARLY`), existence.
+- **User-owned** (seeded once on insert, never touched again by sync):
+  location, reminders, notes, busy/free.
+
+The rule that makes this safe: sync performs a **targeted column update**
+(managed columns only), **never delete-and-reinsert**. Reminders live in
+separate rows, so once seeded they are simply never re-touched. A user can move
+a birthday reminder to "2 weeks before" or add a location and neither is
+clobbered.
+
+In the editor, when an event belongs to a managed calendar: disable the
+title/date/recurrence fields; allow the rest.
+
+### Reconciliation identity
+
+Stamp each event with the contact's `LOOKUP_KEY` in `Events.SYNC_DATA1` (ours,
+since it's a local calendar). Sync becomes an idempotent diff keyed on it:
+
+- contact added → insert
+- birthday/date changed → targeted update of managed columns
+- contact or date removed → delete the event
+
+Getting this wrong = duplicate birthdays on every sync, so the identity key is
+non-negotiable.
+
+### Data source
+
+`ContactsContract.Data` rows of `Event.CONTENT_ITEM_TYPE`, split by
+`Event.TYPE`:
+
+- `TYPE_BIRTHDAY` → Birthdays calendar
+- `TYPE_ANNIVERSARY` → Anniversaries calendar
+- `TYPE_OTHER` / `TYPE_CUSTOM` (+ label) → Custom dates calendar
+
+### Dates: year-less + age
+
+Many contacts store `--MM-DD` (no year). Handle both:
+
+- **Year present:** anchor `DTSTART` at that year; `FREQ=YEARLY`. We can show
+  age ("Jane turns 30") when the show-age option is on.
+- **Year absent:** `FREQ=YEARLY` from an arbitrary anchor year; no age shown.
+
+Recurrence support is already there: `FREQ=YEARLY` + `UNTIL`/`COUNT`/`INTERVAL`
+(`Recurrence.kt:32-174`).
+
+### Auto-update cadence
+
+Birthdays change rarely, so nothing live/expensive:
+
+- Sync **on enable**, **on app foreground**, and a **daily WorkManager** job
+  (catches new/edited/deleted contacts even if the app isn't opened).
+- **No `ContentObserver`** — needs the process alive and buys almost nothing
+  for once-a-year events.
+
+### Permission + lifecycle
+
+- **Enable:** request `READ_CONTACTS` (feature-gated, contextual — mirror the
+  contextual `WRITE_CALENDAR` pattern at `EventEditScreen.kt:216-231`). On
+  grant, create the enabled calendars and run the first sync.
+- **Disable:** delete the managed calendars + their events (with a confirm).
+- **Permission revoked in system settings:** detect on next sync; surface that
+  the feature is stalled rather than failing silently.
+
+### Configurable settings sub-page
+
+Enabling the feature reveals a **dedicated sub-page** (not inline rows). Because
+color/visibility/reminders already live in normal calendar settings, the
+sub-page only carries the genuinely new knobs:
+
+- Master enable toggle.
+- Per-type toggles: Birthdays / Anniversaries / Custom dates.
+- Title/display template, e.g. `"{name}'s birthday"` (new translatable string).
+- Show-age toggle (only meaningful when the year is known).
+- (Possibly) sync-cadence / "sync now".
+- Pointer to the normal calendar settings for color, visibility, reminders.
+
+The owner wants this broadly configurable — keep the sub-page the home for
+display/behaviour options, and lean on existing per-calendar settings for the
+rest.
+
+---
+
+## Open questions / deferred
+
+- Title template: free-form vs a small set of presets. Start with one good
+  localized default; revisit configurability.
+- Whether "Custom dates" is one bucket or split further by label. Start: one
+  bucket.
+- Contact scope: all contacts vs per-account/group filtering. Start: all;
+  filtering is a later refinement.
+
+## Task outline
+
+### #14 — per-calendar multiple default reminders (`feat/per-calendar-multi-reminders`)
+- [x] Widen global + per-calendar reminder defaults `Int` → `List<Int>`
+      (`SettingsPrefs.kt`), keep `Inherit/None/Minutes(list)`.
+- [x] `resolveDefaultReminder()` returns a list.
+- [x] `ReminderDefaultPicker` → multi-select (mirror event-form UI).
+- [x] Seed new events' `EventForm.reminders` from the resolved list.
+- [x] Migration / parse compatibility for existing single-value stored prefs.
+- [x] Tests: resolution, parse round-trip, all-day variant.
+
+### #15 — contact special-dates (`feat/contact-special-dates`)
+- [x] Declare `READ_CONTACTS`; feature-gated contextual request on enable.
+- [x] Per-type local calendars (create on enable, delete on disable+confirm).
+- [x] Contacts reader: `Event` rows by `TYPE`, year-less handling.
+- [x] Sync engine: idempotent diff keyed on the deterministic `UID_2445`
+      (see notes; not `SYNC_DATA1`); targeted managed-column updates; seed
+      user-owned fields on insert only.
+- [x] `FREQ=YEARLY` event generation + age (when year known; sync-time snapshot).
+- [x] Auto-update: on enable, on foreground, daily WorkManager.
+- [x] Editor: disable managed fields for managed-calendar events.
+- [x] Revoked-permission detection + stalled-state surface.
+- [x] Settings sub-page: enable, per-type toggles, title template, show-age.
+- [x] Translatable strings (titles, sub-page).
+- [x] About / store copy for the optional `READ_CONTACTS` permission.

fastlane/metadata/android/de-DE/full_description.txt

@@ -10,6 +10,12 @@ Serie) und einem einfachen Wiederholungs-Picker. Erinnerungen stellt
 Calendula selbst als Benachrichtigung zu — ein Tipp darauf öffnet den
 Termin.
 
+Optional lassen sich Geburtstage, Jahrestage und weitere besondere Tage
+deiner Kontakte im Kalender anzeigen. Du schaltest das selbst ein; Kontakte
+werden nur auf deinem Gerät gelesen, nie hochgeladen und nie verändert —
+Calendula spiegelt die Daten lediglich in lokale Kalender, die du voll
+kontrollierst.
+
 Der Unterschied liegt im Design: echtes Material 3 Expressive durchgehend,
 mit Dynamic Color, expressiven Animationen und neuen Shape-Sprachen.
 

fastlane/metadata/android/en-US/full_description.txt

@@ -8,6 +8,11 @@ changes (only this event / this and all following / the whole series) and a
 simple repeat picker. Calendula also delivers your event reminders as
 notifications — tap one and you're on the event.
 
+Optionally, show your contacts' birthdays, anniversaries and other special
+dates in your calendar. You turn this on yourself; contacts are read only on
+your device, are never uploaded, and are never changed — Calendula only
+mirrors the dates into local calendars you fully control.
+
 The differentiator is the design: real Material 3 Expressive throughout,
 with dynamic color, expressive motion, and expressive shapes.