diff --git a/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/RobotTestRule.kt b/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/RobotTestRule.kt
index 94e7352b9..9ef4ca353 100644
--- a/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/RobotTestRule.kt
+++ b/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/RobotTestRule.kt
@@ -60,6 +60,7 @@ class RobotTestRule(
         return RuleChain
             .outerRule(HiltAndroidAutoInjectRule(testInstance))
             .around(CoroutinesTestRule())
+            .around(TimeZoneTestRule())
             .around(object : TestWatcher() {
                 override fun starting(description: Description) {
                     // To see logs in the console
diff --git a/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/TimeZoneTestRule.kt b/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/TimeZoneTestRule.kt
new file mode 100644
index 000000000..8b9f13b2f
--- /dev/null
+++ b/core/testing/src/main/java/io/github/droidkaigi/confsched2023/testing/TimeZoneTestRule.kt
@@ -0,0 +1,12 @@
+package io.github.droidkaigi.confsched2023.testing
+
+import org.junit.rules.TestWatcher
+import org.junit.runner.Description
+import java.util.TimeZone
+
+class TimeZoneTestRule : TestWatcher() {
+    override fun starting(description: Description) {
+        super.starting(description)
+        TimeZone.setDefault(TimeZone.getTimeZone("Asia/Tokyo"))
+    }
+}