diff --git a/application/Calendar/CalendarModel.php b/application/Calendar/CalendarModel.php
index 01e9cd613..d68c9ecbf 100644
--- a/application/Calendar/CalendarModel.php
+++ b/application/Calendar/CalendarModel.php
@@ -92,6 +92,19 @@ class CalendarModel
         $unixtimestamp = $date->getTimestamp() + $cest;
         return date('Y-m-d H:i:s', $unixtimestamp);
     }
+    public static function convertMillisecondsToTimestamp($milliseconds)
+    {
+        $timestamp = $milliseconds / 1000;
+        $date = new DateTime();
+        $date->setTimestamp($timestamp);
+        $date->setTimezone(new DateTimeZone('Europe/Berlin'));
+        if ($date->format('I') == 1) {
+            $offset = 7200;
+        } else {
+            $offset = 3600;
+        }
+        return $timestamp - $offset;
+    }
 
     public static function replace_unicode_sequences($string)
     {
@@ -646,12 +659,8 @@ WHERE `TimerecordingCategory`.`hourday`!='1' AND `TimerecordingCategory`.`hourda
 
     public static function updateCalendarEvent($r, $me)
     {
-        $description = ($r->description);
-        $attachments = ($r->attachments);
-        $location = ($r->location);
-        $title = ($r->title);
-        $start = ((($r->start - 7200000) / 1000));
-        $end = ((($r->end - 7200000) / 1000));
+        $start = CalendarModel::convertMillisecondsToTimestamp($r->start);
+        $end = CalendarModel::convertMillisecondsToTimestamp($r->end);
 
 
         if ($title) {