diff --git a/feature/announcement/src/main/java/io/github/droidkaigi/confsched2022/feature/announcement/Announcements.kt b/feature/announcement/src/main/java/io/github/droidkaigi/confsched2022/feature/announcement/Announcements.kt
index 82547aa89..b479576d8 100644
--- a/feature/announcement/src/main/java/io/github/droidkaigi/confsched2022/feature/announcement/Announcements.kt
+++ b/feature/announcement/src/main/java/io/github/droidkaigi/confsched2022/feature/announcement/Announcements.kt
@@ -265,10 +265,13 @@ private fun LocalDate.convertString(): String {
     } else if (this.compareTo(yesterday) == 0) {
         stringResource(Strings.announcement_content_header_title_yesterday)
     } else {
-        "${this.year}/${this.month.value.toString().padStart(2, '0')}/${this.dayOfMonth}"
+        "${this.year}/${this.month.value.padDayOrMonth()}/${this.dayOfMonth.padDayOrMonth()}"
     }
 }
 
+private fun Int.padDayOrMonth(): String =
+    this.toString().padStart(2, '0')
+
 @Preview(showBackground = true)
 @Composable
 fun AnnouncementsPreview() {