Fatal error: Uncaught Error: Interface "ilDatePeriod" not found in /var/www/html/ilias/components/ILIAS/Calendar/classes/Booking/class.ilBookingPeriod.php:12 Stack trace: #0 {main} thrown in /var/www/html/ilias/components/ILIAS/Calendar/classes/Booking/class.ilBookingPeriod.php on line 12