From 8f044685da46e25b3e7d8cf6212df04e714a8f02 Mon Sep 17 00:00:00 2001
From: Phil Davis <phil@jankaritech.com>
Date: Thu, 9 May 2024 15:37:29 +0545
Subject: [PATCH] Handle summer time start for weekly recurrences

---
 lib/Recur/RRuleIterator.php               | 16 ++++++
 tests/VObject/Recur/RRuleIteratorTest.php | 62 ++++++++++++++++++++++-
 2 files changed, 76 insertions(+), 2 deletions(-)

diff --git a/lib/Recur/RRuleIterator.php b/lib/Recur/RRuleIterator.php
index 5af57c77..e5190f06 100644
--- a/lib/Recur/RRuleIterator.php
+++ b/lib/Recur/RRuleIterator.php
@@ -373,7 +373,23 @@ protected function nextDaily(): void
     protected function nextWeekly(): void
     {
         if (!$this->byHour && !$this->byDay) {
+            $hourOfCurrentDate = (int) $this->currentDate->format('G');
             $this->currentDate = $this->currentDate->modify('+'.$this->interval.' weeks');
+            $hourOfNextDate = (int) $this->currentDate->format('G');
+            if (0 === $this->hourJump) {
+                // Remember if the clock time jumped forward on the nextDate.
+                // That happens if nextDate is a day when summer time starts
+                // and the event time is in the non-existent hour of the day.
+                // For example, an event that normally starts at 02:30 will
+                // have to start at 03:30 on that day.
+                $this->hourJump = $hourOfNextDate - $hourOfCurrentDate;
+            } else {
+                // The hour "jumped" for the previous date, to avoid the non-existent time.
+                // currentDate got set ahead by (usually) one hour on that day.
+                // Adjust it back for this next occurrence.
+                $this->currentDate = $this->currentDate->sub(new \DateInterval('PT'.$this->hourJump.'H'));
+                $this->hourJump = 0;
+            }
 
             return;
         }
diff --git a/tests/VObject/Recur/RRuleIteratorTest.php b/tests/VObject/Recur/RRuleIteratorTest.php
index 6771bea0..6739ed6c 100644
--- a/tests/VObject/Recur/RRuleIteratorTest.php
+++ b/tests/VObject/Recur/RRuleIteratorTest.php
@@ -163,7 +163,7 @@ public function testDailyBySetPosLoop(): void
     }
 
     /**
-     * @dataProvider dstTransitionProvider
+     * @dataProvider dstDailyTransitionProvider
      */
     public function testDailyOnDstTransition(string $start, array $expected): void
     {
@@ -176,7 +176,7 @@ public function testDailyOnDstTransition(string $start, array $expected): void
         );
     }
 
-    public function dstTransitionProvider(): iterable
+    public function dstDailyTransitionProvider(): iterable
     {
         yield 'On transition start' => [
             'Start' => '2023-03-24 02:00:00',
@@ -323,6 +323,64 @@ public function testWeeklyByDaySpecificHour(): void
         );
     }
 
+    /**
+     * @dataProvider dstWeeklyTransitionProvider
+     */
+    public function testWeeklyOnDstTransition(string $start, array $expected): void
+    {
+        $this->parse(
+            'FREQ=WEEKLY;INTERVAL=1;COUNT=5',
+            $start,
+            $expected,
+            null,
+            'Europe/Zurich',
+        );
+    }
+
+    public function dstWeeklyTransitionProvider(): iterable
+    {
+        yield 'On transition start' => [
+            'Start' => '2023-03-12 02:00:00',
+            'Expected' => [
+                '2023-03-12 02:00:00',
+                '2023-03-19 02:00:00',
+                '2023-03-26 03:00:00',
+                '2023-04-02 02:00:00',
+                '2023-04-09 02:00:00',
+            ],
+        ];
+        yield 'During transition' => [
+            'Start' => '2023-03-12 02:15:00',
+            'Expected' => [
+                '2023-03-12 02:15:00',
+                '2023-03-19 02:15:00',
+                '2023-03-26 03:15:00',
+                '2023-04-02 02:15:00',
+                '2023-04-09 02:15:00',
+            ],
+        ];
+        yield 'On transition end' => [
+            'Start' => '2023-03-12 03:00:00',
+            'Expected' => [
+                '2023-03-12 03:00:00',
+                '2023-03-19 03:00:00',
+                '2023-03-26 03:00:00',
+                '2023-04-02 03:00:00',
+                '2023-04-09 03:00:00',
+            ],
+        ];
+        yield 'After transition end' => [
+            'Start' => '2023-03-12 03:15:00',
+            'Expected' => [
+                '2023-03-12 03:15:00',
+                '2023-03-19 03:15:00',
+                '2023-03-26 03:15:00',
+                '2023-04-02 03:15:00',
+                '2023-04-09 03:15:00',
+            ],
+        ];
+    }
+
     public function testMonthly(): void
     {
         $this->parse(