Fix broken month view if last week of December is in next year

The cause was using the wrong character in formatting the year.
We now switch from `Y` to `o` which will work based on the week instead
of date. This is necessary as we provide this year to the week, and
therefore need the year of the week, not day.

Resolves: #11388

Classes/Domain/Model/Month.php

@@ -78,7 +78,7 @@ public function getWeeks(): array
         while ($currentDay <= $lastDay) {
             $this->weeks[] = new Week(
                 (int) $currentDay->format('W'),
-                (int) $currentDay->format('Y')
+                (int) $currentDay->format('o')
             );
 
             $currentDay = $currentDay->modify('+7 days');

Classes/Domain/Model/Week.php

@@ -80,7 +80,7 @@ public function getPreviousWeek(): Week
 
         return new self(
             (int) $newDay->format('W'),
-            (int) $newDay->format('Y')
+            (int) $newDay->format('o')
         );
     }
 
@@ -90,7 +90,7 @@ public function getNextWeek(): Week
 
         return new self(
             (int) $newDay->format('W'),
-            (int) $newDay->format('Y')
+            (int) $newDay->format('o')
         );
     }
 

Documentation/Changelog/1.1.1.rst

@@ -14,7 +14,12 @@ Nothing
 Fixes
 -----
 
-Nothing
+* Fix broken month view if last week of December is in next year.
+
+  The cause was using the wrong character in formatting the year.
+  We now switch from `Y` to `o` which will work based on the week instead of date.
+  This is necessary as we provide this year to the week,
+  and therefore need the year of the week, not day.
 
 Tasks
 -----

Tests/Unit/Domain/Model/MonthTest.php

@@ -138,6 +138,28 @@ public function returnsAllDaysOfTheFebruaryMonth2021(): void
         self::assertSame('2021-02-28', $result[27]->getDateTimeInstance()->format('Y-m-d'));
     }
 
+    /**
+     * @test
+     */
+    public function returnsWeeksIfLastDecemberWeekIsInNextYear(): void
+    {
+        $subject = new Month(12, 2024);
+
+        $result = $subject->getWeeks();
+
+        self::assertCount(6, $result);
+
+        $week = array_pop($result);
+        $days = $week->getDays();
+        self::assertSame('2024-12-30', $days[0]->getDateTimeInstance()->format('Y-m-d'));
+        self::assertSame('2025-01-05', $days[6]->getDateTimeInstance()->format('Y-m-d'));
+
+        $week = array_pop($result);
+        $days = $week->getDays();
+        self::assertSame('2024-12-23', $days[0]->getDateTimeInstance()->format('Y-m-d'));
+        self::assertSame('2024-12-29', $days[6]->getDateTimeInstance()->format('Y-m-d'));
+    }
+
     /**
      * @test
      */