Weird timezone issue

I’m creating an array from dates of a children collection with a page model. Each page has a start and an end date. After creating date objects some of them have GMT+1 and others have GMT+2. Even though the timezone is set…
date_default_timezone_set('Europe/Zurich');

The page model looks like:

  public function bookedRange(array $rooms = null)
  {
    $dates = [];
    
    $bookings = page('bookings')->children();
    
    foreach ($bookings as $booking) {
      $timezone = new DateTimeZone(date_default_timezone_get());
      $start = new Date($booking->start()->toDate(),$timezone);
      $end = new Date($booking->end()->toDate(),$timezone);       
      $now = new Date(Date('Y-m-d'));
      $dates[] = [
        'from' => $start,
        'to' => $end,
        'created' => $booking->published('%Y-%m-%d %H:%M:%S')
      ];
    }

    return $dates;
  }

And it outputs the following array:

Array
(
    [0] => Array
        (
            [from] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-08-22 15:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [to] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-08-28 10:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [created] => Kirby\Cms\Field Object
                (
                    [published] => 
                )

        )

    [1] => Array
        (
            [from] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-09-19 15:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [to] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-09-25 10:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [created] => Kirby\Cms\Field Object
                (
                    [published] => 
                )

        )

    [2] => Array
        (
            [from] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-12-12 15:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +01:00
                )

            [to] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-12-25 10:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +01:00
                )

            [created] => Kirby\Cms\Field Object
                (
                    [published] => 
                )

        )

    [3] => Array
        (
            [from] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-08-28 15:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [to] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-08-31 10:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [created] => Kirby\Cms\Field Object
                (
                    [published] => 
                )

        )

    [4] => Array
        (
            [from] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-09-03 15:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [to] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-09-04 10:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [created] => Kirby\Cms\Field Object
                (
                    [published] => 
                )

        )

    [5] => Array
        (
            [from] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-10-10 15:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [to] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-10-16 10:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [created] => Kirby\Cms\Field Object
                (
                    [published] => 
                )

        )

    [6] => Array
        (
            [from] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-11-01 15:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +01:00
                )

            [to] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-11-06 10:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +01:00
                )

            [created] => Kirby\Cms\Field Object
                (
                    [published] => 
                )

        )

    [7] => Array
        (
            [from] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-09-10 15:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [to] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-09-17 10:00:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [created] => Kirby\Cms\Field Object
                (
                    [published] => 
                )

        )

    [8] => Array
        (
            [from] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-08-19 16:45:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [to] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-08-22 16:45:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [created] => Kirby\Cms\Field Object
                (
                    [published] => 
                )

        )

    [9] => Array
        (
            [from] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-08-02 22:30:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [to] => Kirby\Toolkit\Date Object
                (
                    [date] => 2022-08-17 22:30:00.000000
                    [timezone_type] => 1
                    [timezone] => +02:00
                )

            [created] => Kirby\Cms\Field Object
                (
                    [published] => 
                )

        )

)

Can someone help me to rule the timezones?

BTW: If I remove the timzone definition date_default_timezone_set('Europe/Zurich'); then it outputs for every time +00:00

My guess would be summer vs winter time?

You are right. Just realised it :see_no_evil:
It this f***ing time change…