diff --git a/internal/sub/calendar_expire_test.go b/internal/sub/calendar_expire_test.go
index 281dd7383..2d611e54a 100644
--- a/internal/sub/calendar_expire_test.go
+++ b/internal/sub/calendar_expire_test.go
@@ -37,8 +37,9 @@ func TestSubscriptionCalendarExpireInclusive(t *testing.T) {
 		{"Taipei midnight", "true", "Asia/Taipei", "2030-10-01T00:00:00+08:00", 1, 1, true},
 		{"New York daylight time", "true", "America/New_York", "2030-10-01T00:00:00-04:00", 1, 1, true},
 		{"New York standard time", "true", "America/New_York", "2030-02-01T00:00:00-05:00", 1, 1, true},
-		{"Havana first midnight", "true", "America/Havana", "2026-11-01T00:00:00-04:00", 1, 1, true},
-		{"Havana repeated midnight", "true", "America/Havana", "2026-11-01T00:00:00-05:00", 1, 1, false},
+		// Past fallback on purpose: tzdata 2026f cancelled Cuba's 2026 one.
+		{"Havana first midnight", "true", "America/Havana", "2020-11-01T00:00:00-04:00", 1, 1, true},
+		{"Havana repeated midnight", "true", "America/Havana", "2020-11-01T00:00:00-05:00", 1, 1, false},
 		{"UTC midnight is not Taipei midnight", "true", "Asia/Taipei", "2030-10-01T00:00:00Z", 1, 1, false},
 		{"midday unchanged", "true", "UTC", "2030-10-01T12:00:00Z", 1, 1, false},
 		{"other midnight unchanged", "true", "UTC", "2030-10-02T00:00:00Z", 1, 1, false},
diff --git a/internal/web/service/calendar_weekly_renew_test.go b/internal/web/service/calendar_weekly_renew_test.go
index c42a92b7f..eb6ce35a2 100644
--- a/internal/web/service/calendar_weekly_renew_test.go
+++ b/internal/web/service/calendar_weekly_renew_test.go
@@ -10,10 +10,12 @@ func TestNextWeeklyRenewal_RepeatedMidnight(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	// A past transition: tzdata 2026f cancelled Cuba's November 2026 fallback,
+	// so a future one makes the result depend on the host's tzdata version.
 	for _, tt := range []struct{ expiry, want string }{
-		{"2026-10-25T00:00:00-04:00", "2026-11-01T00:00:00-04:00"},
-		{"2026-11-01T00:00:00-04:00", "2026-11-08T00:00:00-05:00"},
-		{"2026-11-01T00:00:00-05:00", "2026-11-08T00:00:00-05:00"},
+		{"2020-10-25T00:00:00-04:00", "2020-11-01T00:00:00-04:00"},
+		{"2020-11-01T00:00:00-04:00", "2020-11-08T00:00:00-05:00"},
+		{"2020-11-01T00:00:00-05:00", "2020-11-08T00:00:00-05:00"},
 	} {
 		from, err := time.Parse(time.RFC3339, tt.expiry)
 		if err != nil {