diff --git a/app-android/src/main/java/io/github/droidkaigi/confsched2023/AppModule.kt b/app-android/src/main/java/io/github/droidkaigi/confsched2023/AppModule.kt
index 06b477e0d..1b555fd33 100644
--- a/app-android/src/main/java/io/github/droidkaigi/confsched2023/AppModule.kt
+++ b/app-android/src/main/java/io/github/droidkaigi/confsched2023/AppModule.kt
@@ -6,6 +6,7 @@ import dagger.hilt.InstallIn
 import dagger.hilt.components.SingletonComponent
 import io.github.droidkaigi.confsched2023.data.di.AppAndroidBuildConfig
 import io.github.droidkaigi.confsched2023.model.BuildConfigProvider
+import kotlinx.datetime.Clock
 import javax.inject.Singleton
 
 @InstallIn(SingletonComponent::class)
@@ -15,9 +16,19 @@ class AppModule {
     @Singleton
     @AppAndroidBuildConfig
     fun provideBuildConfigProvider(): BuildConfigProvider = AppBuildConfigProvider()
+
+    @Provides
+    @Singleton
+    fun provideClockProvider(): ClockProvider = object : ClockProvider {
+        override fun clock(): Clock = Clock.System
+    }
 }
 
 class AppBuildConfigProvider(
     override val versionName: String = BuildConfig.VERSION_NAME,
     override val debugBuild: Boolean = BuildConfig.DEBUG,
 ) : BuildConfigProvider
+
+interface ClockProvider {
+    fun clock(): Clock
+}
diff --git a/app-android/src/main/java/io/github/droidkaigi/confsched2023/MainActivity.kt b/app-android/src/main/java/io/github/droidkaigi/confsched2023/MainActivity.kt
index 83aff3ba3..e7d5bb352 100644
--- a/app-android/src/main/java/io/github/droidkaigi/confsched2023/MainActivity.kt
+++ b/app-android/src/main/java/io/github/droidkaigi/confsched2023/MainActivity.kt
@@ -10,6 +10,7 @@ import androidx.activity.enableEdgeToEdge
 import androidx.compose.material3.windowsizeclass.ExperimentalMaterial3WindowSizeClassApi
 import androidx.compose.material3.windowsizeclass.calculateWindowSizeClass
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.produceState
 import androidx.compose.runtime.remember
@@ -19,12 +20,18 @@ import androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen
 import androidx.window.layout.DisplayFeature
 import androidx.window.layout.WindowInfoTracker
 import dagger.hilt.android.AndroidEntryPoint
+import io.github.droidkaigi.confsched2023.ui.compositionlocal.LocalClock
 import kotlinx.collections.immutable.PersistentList
 import kotlinx.collections.immutable.persistentListOf
 import kotlinx.collections.immutable.toPersistentList
+import javax.inject.Inject
 
 @AndroidEntryPoint
 class MainActivity : ComponentActivity() {
+
+    @Inject
+    lateinit var clockProvider: ClockProvider
+
     @OptIn(ExperimentalMaterial3WindowSizeClassApi::class)
     override fun onCreate(savedInstanceState: Bundle?) {
         installSplashScreen()
@@ -55,10 +62,12 @@ class MainActivity : ComponentActivity() {
         setContent {
             val windowSize = calculateWindowSizeClass(this)
             val displayFeatures = calculateDisplayFeatures(this)
-            KaigiApp(
-                windowSize = windowSize,
-                displayFeatures = displayFeatures,
-            )
+            CompositionLocalProvider(LocalClock provides clockProvider.clock()) {
+                KaigiApp(
+                    windowSize = windowSize,
+                    displayFeatures = displayFeatures,
+                )
+            }
         }
     }
 }
diff --git a/app-android/src/test/java/io/github/droidkaigi/confsched2023/FakeAppModule.kt b/app-android/src/test/java/io/github/droidkaigi/confsched2023/FakeAppModule.kt
new file mode 100644
index 000000000..90ddc1f3b
--- /dev/null
+++ b/app-android/src/test/java/io/github/droidkaigi/confsched2023/FakeAppModule.kt
@@ -0,0 +1,24 @@
+package io.github.droidkaigi.confsched2023
+
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.components.SingletonComponent
+import dagger.hilt.testing.TestInstallIn
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+import javax.inject.Singleton
+
+@TestInstallIn(
+    components = [SingletonComponent::class],
+    replaces = [AppModule::class],
+)
+@Module
+class FakeAppModule {
+    @Provides
+    @Singleton
+    fun provideClockProvider(): ClockProvider = object : ClockProvider {
+        override fun clock(): Clock = object : Clock {
+            override fun now() = Instant.parse("2023-09-14T10:00:00.00Z")
+        }
+    }
+}
diff --git a/core/model/src/commonMain/kotlin/io/github/droidkaigi/confsched2023/model/DroidKaigi2023Day.kt b/core/model/src/commonMain/kotlin/io/github/droidkaigi/confsched2023/model/DroidKaigi2023Day.kt
index ac3feab49..0648b9948 100644
--- a/core/model/src/commonMain/kotlin/io/github/droidkaigi/confsched2023/model/DroidKaigi2023Day.kt
+++ b/core/model/src/commonMain/kotlin/io/github/droidkaigi/confsched2023/model/DroidKaigi2023Day.kt
@@ -81,14 +81,11 @@ public enum class DroidKaigi2023Day(
         /**
          * @return appropriate initial day for now
          */
-        fun initialSelectedDay(isTest: Boolean = false): DroidKaigi2023Day {
-            // Timetable tab set initial tab with current date.
-            // To get the consistent test result, fix selected timetable tab to Day1 here.
-            if (isTest) return Day1
+        fun initialSelectedDay(clock: Clock): DroidKaigi2023Day {
             val reversedEntries = entries.sortedByDescending { it.day }
             var selectedDay = reversedEntries.last()
             for (entry in reversedEntries) {
-                if (Clock.System.now() <= entry.end) selectedDay = entry
+                if (clock.now() <= entry.end) selectedDay = entry
             }
             return selectedDay
         }
diff --git a/core/testing/build.gradle.kts b/core/testing/build.gradle.kts
index 8016717c1..2d65923e5 100644
--- a/core/testing/build.gradle.kts
+++ b/core/testing/build.gradle.kts
@@ -12,6 +12,7 @@ dependencies {
     implementation(projects.core.model)
     implementation(projects.core.designsystem)
     implementation(projects.core.data)
+    implementation(projects.core.ui)
     implementation(projects.feature.main)
     implementation(projects.feature.sessions)
     implementation(projects.feature.about)
diff --git a/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/robot/TimetableScreenRobot.kt b/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/robot/TimetableScreenRobot.kt
index 1bea2ec3e..e68f65f2a 100644
--- a/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/robot/TimetableScreenRobot.kt
+++ b/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/robot/TimetableScreenRobot.kt
@@ -1,5 +1,6 @@
 package io.github.droidkaigi.confsched2023.testing.robot
 
+import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.ui.test.assertIsDisplayed
 import androidx.compose.ui.test.hasTestTag
 import androidx.compose.ui.test.isRoot
@@ -25,6 +26,8 @@ import io.github.droidkaigi.confsched2023.sessions.component.TimetableUiTypeChan
 import io.github.droidkaigi.confsched2023.sessions.section.TimetableTabTestTag
 import io.github.droidkaigi.confsched2023.testing.RobotTestRule
 import io.github.droidkaigi.confsched2023.testing.coroutines.runTestWithLogging
+import io.github.droidkaigi.confsched2023.ui.compositionlocal.FakeClock
+import io.github.droidkaigi.confsched2023.ui.compositionlocal.LocalClock
 import kotlinx.coroutines.test.TestDispatcher
 import javax.inject.Inject
 import kotlin.time.Duration.Companion.seconds
@@ -50,12 +53,14 @@ class TimetableScreenRobot @Inject constructor(
 
     fun setupTimetableScreenContent() {
         composeTestRule.setContent {
-            KaigiTheme {
-                TimetableScreen(
-                    onSearchClick = { },
-                    onTimetableItemClick = { },
-                    onBookmarkIconClick = { },
-                )
+            CompositionLocalProvider(LocalClock provides FakeClock) {
+                KaigiTheme {
+                    TimetableScreen(
+                        onSearchClick = { },
+                        onTimetableItemClick = { },
+                        onBookmarkIconClick = { },
+                    )
+                }
             }
         }
         waitUntilIdle()
diff --git a/core/ui/build.gradle.kts b/core/ui/build.gradle.kts
index a396e8521..48e34b842 100644
--- a/core/ui/build.gradle.kts
+++ b/core/ui/build.gradle.kts
@@ -18,6 +18,7 @@ kotlin {
                 implementation(libs.kermit)
                 api(projects.core.common)
                 api(libs.composeImageLoader)
+                api(libs.kotlinxDatetime)
             }
         }
     }
diff --git a/core/ui/src/androidMain/kotlin/io/github/droidkaigi/confsched2023/ui/compositionlocal/LocalClock.kt b/core/ui/src/androidMain/kotlin/io/github/droidkaigi/confsched2023/ui/compositionlocal/LocalClock.kt
new file mode 100644
index 000000000..0cb30ce7f
--- /dev/null
+++ b/core/ui/src/androidMain/kotlin/io/github/droidkaigi/confsched2023/ui/compositionlocal/LocalClock.kt
@@ -0,0 +1,14 @@
+package io.github.droidkaigi.confsched2023.ui.compositionlocal
+
+import androidx.compose.runtime.staticCompositionLocalOf
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+
+@Suppress("CompositionLocalAllowlist")
+val LocalClock = staticCompositionLocalOf<Clock> {
+    Clock.System
+}
+
+object FakeClock : Clock {
+    override fun now(): Instant = Instant.parse("2023-09-14T10:00:00.000Z")
+}
diff --git a/feature/sessions/src/main/java/io/github/droidkaigi/confsched2023/sessions/TimetableScreen.kt b/feature/sessions/src/main/java/io/github/droidkaigi/confsched2023/sessions/TimetableScreen.kt
index 545dc4330..1a48a09d1 100644
--- a/feature/sessions/src/main/java/io/github/droidkaigi/confsched2023/sessions/TimetableScreen.kt
+++ b/feature/sessions/src/main/java/io/github/droidkaigi/confsched2023/sessions/TimetableScreen.kt
@@ -16,6 +16,7 @@ import androidx.compose.material3.Scaffold
 import androidx.compose.material3.SnackbarHost
 import androidx.compose.material3.SnackbarHostState
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.ReadOnlyComposable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
@@ -51,6 +52,8 @@ import io.github.droidkaigi.confsched2023.sessions.section.TimetableListUiState
 import io.github.droidkaigi.confsched2023.sessions.section.TimetableSheet
 import io.github.droidkaigi.confsched2023.sessions.section.TimetableSheetUiState
 import io.github.droidkaigi.confsched2023.ui.SnackbarMessageEffect
+import io.github.droidkaigi.confsched2023.ui.compositionlocal.FakeClock
+import io.github.droidkaigi.confsched2023.ui.compositionlocal.LocalClock
 import kotlinx.collections.immutable.toPersistentMap
 import kotlin.math.roundToInt
 
@@ -249,32 +252,34 @@ private fun TimetableScreen(
 @MultiThemePreviews
 @Composable
 fun PreviewTimetableScreenDark() {
-    KaigiTheme {
-        TimetableScreen(
-            uiState = TimetableScreenUiState(
-                contentUiState = TimetableSheetUiState.ListTimetable(
-                    mapOf(
-                        DroidKaigi2023Day.Day1 to TimetableListUiState(
-                            mapOf<String, List<TimetableItem>>().toPersistentMap(),
-                            Timetable(),
-                        ),
-                        DroidKaigi2023Day.Day2 to TimetableListUiState(
-                            mapOf<String, List<TimetableItem>>().toPersistentMap(),
-                            Timetable(),
+    CompositionLocalProvider(LocalClock provides FakeClock) {
+        KaigiTheme {
+            TimetableScreen(
+                uiState = TimetableScreenUiState(
+                    contentUiState = TimetableSheetUiState.ListTimetable(
+                        mapOf(
+                            DroidKaigi2023Day.Day1 to TimetableListUiState(
+                                mapOf<String, List<TimetableItem>>().toPersistentMap(),
+                                Timetable(),
+                            ),
+                            DroidKaigi2023Day.Day2 to TimetableListUiState(
+                                mapOf<String, List<TimetableItem>>().toPersistentMap(),
+                                Timetable(),
+                            ),
                         ),
                     ),
+                    timetableUiType = TimetableUiType.Grid,
+                    onBookmarkIconClickStatus = false,
                 ),
-                timetableUiType = TimetableUiType.Grid,
-                onBookmarkIconClickStatus = false,
-            ),
-            snackbarHostState = SnackbarHostState(),
-            onTimetableItemClick = {},
-            onBookmarkClick = { _, _ -> },
-            onBookmarkIconClick = {},
-            onSearchClick = {},
-            onTimetableUiChangeClick = {},
-            onReachAnimationEnd = {},
-            modifier = Modifier.statusBarsPadding(),
-        )
+                snackbarHostState = SnackbarHostState(),
+                onTimetableItemClick = {},
+                onBookmarkClick = { _, _ -> },
+                onBookmarkIconClick = {},
+                onSearchClick = {},
+                onTimetableUiChangeClick = {},
+                onReachAnimationEnd = {},
+                modifier = Modifier.statusBarsPadding(),
+            )
+        }
     }
 }
diff --git a/feature/sessions/src/main/java/io/github/droidkaigi/confsched2023/sessions/section/TimetableSheet.kt b/feature/sessions/src/main/java/io/github/droidkaigi/confsched2023/sessions/section/TimetableSheet.kt
index f2e208f73..71925d7b3 100644
--- a/feature/sessions/src/main/java/io/github/droidkaigi/confsched2023/sessions/section/TimetableSheet.kt
+++ b/feature/sessions/src/main/java/io/github/droidkaigi/confsched2023/sessions/section/TimetableSheet.kt
@@ -36,7 +36,7 @@ import io.github.droidkaigi.confsched2023.sessions.component.rememberTimetableTa
 import io.github.droidkaigi.confsched2023.sessions.section.TimetableSheetUiState.Empty
 import io.github.droidkaigi.confsched2023.sessions.section.TimetableSheetUiState.GridTimetable
 import io.github.droidkaigi.confsched2023.sessions.section.TimetableSheetUiState.ListTimetable
-import io.github.droidkaigi.confsched2023.ui.isTest
+import io.github.droidkaigi.confsched2023.ui.compositionlocal.LocalClock
 
 const val TimetableTabTestTag = "TimetableTab"
 
@@ -60,7 +60,8 @@ fun TimetableSheet(
     contentPadding: PaddingValues,
     modifier: Modifier = Modifier,
 ) {
-    var selectedDay by rememberSaveable { mutableStateOf(DroidKaigi2023Day.initialSelectedDay(isTest())) }
+    val clock = LocalClock.current
+    var selectedDay by rememberSaveable { mutableStateOf(DroidKaigi2023Day.initialSelectedDay(clock)) }
     val corner by animateIntAsState(
         if (timetableScreenScrollState.isScreenLayoutCalculating || timetableScreenScrollState.isSheetExpandable) 40 else 0,
         label = "Timetable corner state",