ext/date: trim and expand DST tests for GH-21616 and GH-15880

Remove section headers and redundant cases. Add -72h backward through
fall-back, +61 minutes across spring-forward gap, and DateTimeImmutable.

Author: MarcusXavierr

ext/date/tests/gh15880.phpt

@@ -3,53 +3,26 @@ Bug GH-15880 (DateTime::modify('+72 hours') incorrect across DST boundary)
 --FILE--
 <?php
 /* Fall back: America/Chicago, 2024-11-03 02:00 CDT -> 01:00 CST.
- * +72 hours from 2024-11-01 00:00 CDT must be 2024-11-03 23:00 CST,
- * not 2024-11-04 00:00 CST. */
+ * +72 hours from midnight Nov 1 must land at Nov 3 23:00 CST, not Nov 4 00:00. */
+date_default_timezone_set('America/Chicago');
 $tz = new DateTimeZone('America/Chicago');
-
-echo "=== Fall back (explicit timezone) ===\n";
-
 $start = new DateTimeImmutable('2024-11-01 00:00:00', $tz);
 
-echo "modify +72 hours:\n";
+/* modify and add must agree */
 echo $start->modify('+72 hours')->format('Y-m-d H:i:s T U'), "\n";
+echo $start->add(new DateInterval('PT72H'))->format('Y-m-d H:i:s T U'), "\n";
 
-echo "add PT72H (reference):\n";
-echo $start->add(new DateInterval('PT72H'))
-           ->format('Y-m-d H:i:s T U'), "\n";
-
-echo "\n=== Fall back with default timezone ===\n";
-
-/* Exact reproduction from GH-15880: date_default_timezone_set,
- * DateTimeImmutable, +72 hour via modify vs add. Also test that
- * +3 days (calendar arithmetic) is unaffected — it should land on
- * midnight Nov 4, not Nov 3 23:00. */
-date_default_timezone_set('America/Chicago');
-$start2 = new DateTimeImmutable('2024-11-01');
+/* +3 days is calendar arithmetic -- it should land on midnight Nov 4 */
+echo $start->modify('+3 days')->format('Y-m-d H:i:s T U'), "\n";
 
-echo "modify +72 hour:\n";
-echo $start2->modify('+72 hour')
-            ->format('Y-m-d H:i:s T U'), "\n";
-
-echo "add PT72H (reference):\n";
-echo $start2->add(new DateInterval('PT72H'))
-            ->format('Y-m-d H:i:s T U'), "\n";
-
-echo "modify +3 days (calendar, not hours):\n";
-echo $start2->modify('+3 days')
-            ->format('Y-m-d H:i:s T U'), "\n";
+/* -72 hours backward through fall-back: 73 real hours separate Nov 1 00:00 CDT
+ * from Nov 4 00:00 CST (the extra hour is the repeated hour), so -72h lands 1h
+ * ahead of Nov 1 midnight */
+$end = new DateTimeImmutable('2024-11-04 00:00:00', $tz);
+echo $end->modify('-72 hours')->format('Y-m-d H:i:s T U'), "\n";
 ?>
 --EXPECT--
-=== Fall back (explicit timezone) ===
-modify +72 hours:
-2024-11-03 23:00:00 CST 1730696400
-add PT72H (reference):
-2024-11-03 23:00:00 CST 1730696400
-
-=== Fall back with default timezone ===
-modify +72 hour:
 2024-11-03 23:00:00 CST 1730696400
-add PT72H (reference):
 2024-11-03 23:00:00 CST 1730696400
-modify +3 days (calendar, not hours):
 2024-11-04 00:00:00 CST 1730700000
+2024-11-01 01:00:00 CDT 1730440800

ext/date/tests/gh21616.phpt

@@ -2,65 +2,41 @@
 Bug GH-21616 (DateTime::modify() does not respect DST transitions)
 --FILE--
 <?php
-/* Spring forward: Europe/London, 2025-03-30 01:00 GMT -> 02:00 BST.
- * Subtracting 1 second from 02:00:00 BST must land at 00:59:59 GMT,
- * not at 02:59:59 BST. */
+/* Spring forward: Europe/London, 2025-03-30 01:00 GMT -> 02:00 BST */
 $tz = new DateTimeZone('Europe/London');
 
-echo "=== Spring forward ===\n";
-
-echo "modify +1s then -1s:\n";
+/* +1s then -1s must round-trip */
 $dt = new DateTime('2025-03-30 00:59:59', $tz);
 $dt->modify('+1 second');
 $dt->modify('-1 second');
 echo $dt->format('Y-m-d H:i:s T U'), "\n";
 
-echo "add/sub PT1S (reference):\n";
-$dt2 = new DateTime('2025-03-30 00:59:59', $tz);
-$dt2->add(new DateInterval('PT1S'));
-$dt2->sub(new DateInterval('PT1S'));
-echo $dt2->format('Y-m-d H:i:s T U'), "\n";
-
-echo "modify -1s from 02:00 BST:\n";
-$dt3 = new DateTime('2025-03-30 02:00:00', $tz);
-echo $dt3->modify('-1 second')->format('Y-m-d H:i:s T U'), "\n";
+/* -1s from 02:00 BST must land at 00:59:59 GMT, not 02:59:59 BST */
+$dt2 = new DateTime('2025-03-30 02:00:00', $tz);
+echo $dt2->modify('-1 second')->format('Y-m-d H:i:s T U'), "\n";
 
-echo "\n=== Combined relative (month + hours near DST) ===\n";
+/* month + hours: +1 month lands before the DST boundary, so +1 hour is plain GMT */
+$dt3 = new DateTime('2025-02-28 00:30:00', $tz);
+echo $dt3->modify('+1 month +1 hour')->format('Y-m-d H:i:s T U'), "\n";
 
-/* 2025-02-28 00:30:00 GMT + 1 month + 1 hour should land on
- * 2025-03-28 01:30:00 GMT (not affected by DST on March 30). */
-$dt4 = new DateTime('2025-02-28 00:30:00', $tz);
-echo "modify +1 month +1 hour:\n";
-echo $dt4->modify('+1 month +1 hour')->format('Y-m-d H:i:s T U'), "\n";
+/* first/last day of must still work */
+$base = new DateTimeImmutable('2025-03-15 10:00:00', $tz);
+echo $base->modify('first day of next month')->format('Y-m-d H:i:s T'), "\n";
+echo $base->modify('last day of this month')->format('Y-m-d H:i:s T'), "\n";
 
-echo "\n=== first/last day of (must not regress) ===\n";
+/* +61 minutes from just before the gap -- minutes must also count as elapsed time */
+$dt4 = new DateTime('2025-03-30 00:59:00', $tz);
+echo $dt4->modify('+61 minutes')->format('Y-m-d H:i:s T U'), "\n";
 
-/* Ensure first_last_day_of still works correctly. */
-$dt5 = new DateTime('2025-03-15 10:00:00', $tz);
-echo "modify first day of next month:\n";
-echo $dt5->modify('first day of next month')
-         ->format('Y-m-d H:i:s T'), "\n";
-
-$dt6 = new DateTime('2025-03-15 10:00:00', $tz);
-echo "modify last day of this month:\n";
-echo $dt6->modify('last day of this month')
-         ->format('Y-m-d H:i:s T'), "\n";
+/* DateTimeImmutable must behave the same as mutable DateTime */
+$dt5 = new DateTimeImmutable('2025-03-30 02:00:00', $tz);
+echo $dt5->modify('-1 second')->format('Y-m-d H:i:s T U'), "\n";
 ?>
 --EXPECT--
-=== Spring forward ===
-modify +1s then -1s:
-2025-03-30 00:59:59 GMT 1743296399
-add/sub PT1S (reference):
 2025-03-30 00:59:59 GMT 1743296399
-modify -1s from 02:00 BST:
 2025-03-30 00:59:59 GMT 1743296399
-
-=== Combined relative (month + hours near DST) ===
-modify +1 month +1 hour:
 2025-03-28 01:30:00 GMT 1743125400
-
-=== first/last day of (must not regress) ===
-modify first day of next month:
 2025-04-01 10:00:00 BST
-modify last day of this month:
 2025-03-31 10:00:00 BST
+2025-03-30 03:00:00 BST 1743300000
+2025-03-30 00:59:59 GMT 1743296399