diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/data/di/DataModule.kt b/app/src/main/java/de/jeanlucmakiola/clockula/data/di/DataModule.kt
index eaeca73..dcbd3c6 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/data/di/DataModule.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/data/di/DataModule.kt
@@ -21,8 +21,8 @@ import java.io.File
 import javax.inject.Singleton
 
 /**
- * Clockula's storage bindings. M1 wires the preference half only; the Room
- * database and its DAOs join this module in M2.
+ * The DataStore half of Clockula's storage. The Room database and its DAOs live
+ * next door in `DatabaseModule`.
  */
 @Module
 @InstallIn(SingletonComponent::class)
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/data/di/DatabaseModule.kt b/app/src/main/java/de/jeanlucmakiola/clockula/data/di/DatabaseModule.kt
new file mode 100644
index 0000000..c2f1ed7
--- /dev/null
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/data/di/DatabaseModule.kt
@@ -0,0 +1,42 @@
+package de.jeanlucmakiola.clockula.data.di
+
+import android.content.Context
+import androidx.room.Room
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import de.jeanlucmakiola.clockula.data.alarms.AlarmDao
+import de.jeanlucmakiola.clockula.data.db.ClockulaDatabase
+import de.jeanlucmakiola.clockula.data.stopwatch.LapDao
+import de.jeanlucmakiola.clockula.data.timers.TimerDao
+import de.jeanlucmakiola.clockula.data.worldclocks.WorldClockDao
+import javax.inject.Singleton
+
+/**
+ * The database and its four DAOs. No destructive-migration fallback: docs/PLAN.md
+ * §12 wants every schema change to arrive with a tested migration, and a fallback
+ * would quietly drop a user's alarms instead of failing loudly in review.
+ */
+@Module
+@InstallIn(SingletonComponent::class)
+object DatabaseModule {
+
+    @Provides
+    @Singleton
+    fun provideDatabase(@ApplicationContext context: Context): ClockulaDatabase =
+        Room.databaseBuilder(context, ClockulaDatabase::class.java, ClockulaDatabase.NAME).build()
+
+    @Provides
+    fun provideAlarmDao(database: ClockulaDatabase): AlarmDao = database.alarmDao()
+
+    @Provides
+    fun provideTimerDao(database: ClockulaDatabase): TimerDao = database.timerDao()
+
+    @Provides
+    fun provideWorldClockDao(database: ClockulaDatabase): WorldClockDao = database.worldClockDao()
+
+    @Provides
+    fun provideLapDao(database: ClockulaDatabase): LapDao = database.lapDao()
+}
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/data/di/RepositoryModule.kt b/app/src/main/java/de/jeanlucmakiola/clockula/data/di/RepositoryModule.kt
new file mode 100644
index 0000000..aa12c42
--- /dev/null
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/data/di/RepositoryModule.kt
@@ -0,0 +1,37 @@
+package de.jeanlucmakiola.clockula.data.di
+
+import dagger.Binds
+import dagger.Module
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+import de.jeanlucmakiola.clockula.data.alarms.AlarmRepository
+import de.jeanlucmakiola.clockula.data.alarms.AlarmRepositoryImpl
+import de.jeanlucmakiola.clockula.data.stopwatch.StopwatchRepository
+import de.jeanlucmakiola.clockula.data.stopwatch.StopwatchRepositoryImpl
+import de.jeanlucmakiola.clockula.data.timers.TimerRepository
+import de.jeanlucmakiola.clockula.data.timers.TimerRepositoryImpl
+import de.jeanlucmakiola.clockula.data.worldclocks.WorldClockRepository
+import de.jeanlucmakiola.clockula.data.worldclocks.WorldClockRepositoryImpl
+import javax.inject.Singleton
+
+/** The four interfaces the rest of the app sees — and the only ones it may see. */
+@Module
+@InstallIn(SingletonComponent::class)
+abstract class RepositoryModule {
+
+    @Binds
+    @Singleton
+    abstract fun bindAlarmRepository(impl: AlarmRepositoryImpl): AlarmRepository
+
+    @Binds
+    @Singleton
+    abstract fun bindTimerRepository(impl: TimerRepositoryImpl): TimerRepository
+
+    @Binds
+    @Singleton
+    abstract fun bindWorldClockRepository(impl: WorldClockRepositoryImpl): WorldClockRepository
+
+    @Binds
+    @Singleton
+    abstract fun bindStopwatchRepository(impl: StopwatchRepositoryImpl): StopwatchRepository
+}
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/data/di/TimeModule.kt b/app/src/main/java/de/jeanlucmakiola/clockula/data/di/TimeModule.kt
new file mode 100644
index 0000000..08effc3
--- /dev/null
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/data/di/TimeModule.kt
@@ -0,0 +1,25 @@
+package de.jeanlucmakiola.clockula.data.di
+
+import dagger.Binds
+import dagger.Module
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+import de.jeanlucmakiola.clockula.data.time.SystemElapsedRealtimeClock
+import de.jeanlucmakiola.clockula.data.time.SystemWallClock
+import de.jeanlucmakiola.clockula.domain.time.ElapsedRealtimeClock
+import de.jeanlucmakiola.clockula.domain.time.WallClock
+
+/**
+ * Both clocks are injected, never called statically, so the wall-clock /
+ * elapsed-realtime distinction can be tested from both sides.
+ */
+@Module
+@InstallIn(SingletonComponent::class)
+abstract class TimeModule {
+
+    @Binds
+    abstract fun bindWallClock(impl: SystemWallClock): WallClock
+
+    @Binds
+    abstract fun bindElapsedRealtimeClock(impl: SystemElapsedRealtimeClock): ElapsedRealtimeClock
+}
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/data/time/AndroidClocks.kt b/app/src/main/java/de/jeanlucmakiola/clockula/data/time/AndroidClocks.kt
new file mode 100644
index 0000000..1cb442e
--- /dev/null
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/data/time/AndroidClocks.kt
@@ -0,0 +1,23 @@
+package de.jeanlucmakiola.clockula.data.time
+
+import android.os.SystemClock
+import de.jeanlucmakiola.clockula.domain.time.ElapsedRealtimeClock
+import de.jeanlucmakiola.clockula.domain.time.WallClock
+import kotlin.time.Duration
+import kotlin.time.Duration.Companion.milliseconds
+import kotlin.time.Instant
+import javax.inject.Inject
+
+/** The device's calendar time. Moves with the user, the network and DST. */
+class SystemWallClock @Inject constructor() : WallClock {
+    override fun now(): Instant = Instant.fromEpochMilliseconds(System.currentTimeMillis())
+}
+
+/**
+ * Milliseconds since boot, including deep sleep. Never decreases within a boot
+ * and no setting can move it — which is exactly why a running timer and the
+ * stopwatch anchor on it.
+ */
+class SystemElapsedRealtimeClock @Inject constructor() : ElapsedRealtimeClock {
+    override fun elapsedRealtime(): Duration = SystemClock.elapsedRealtime().milliseconds
+}