diff --git a/lib/models/calendar/CalendarDateAssignment.class.php b/lib/models/calendar/CalendarDateAssignment.class.php
index a5776f70b465c4149be3f583b1cbaf45bed91e0f..670ee22e2c2081b27a15e497a809d31fee76e8b9 100644
--- a/lib/models/calendar/CalendarDateAssignment.class.php
+++ b/lib/models/calendar/CalendarDateAssignment.class.php
@@ -217,6 +217,11 @@ class CalendarDateAssignment extends SimpleORMap implements Event
         bool $with_declined = false
     ) : array
     {
+        // Always use the timezone of the server:
+        $local_timezone = (new DateTime())->getTimezone();
+        $begin->setTimezone($local_timezone);
+        $end->setTimezone($local_timezone);
+
         // one whole day as minimum (begin and end time stamp at the same day)
         $begin->modify('midnight');
         $end->modify('tomorrow -1 second');