diff --git a/lib/ext/Syncroton/Model/EmailMeetingRequest.php b/lib/ext/Syncroton/Model/EmailMeetingRequest.php
--- a/lib/ext/Syncroton/Model/EmailMeetingRequest.php
+++ b/lib/ext/Syncroton/Model/EmailMeetingRequest.php
@@ -68,8 +68,6 @@
     const MESSAGE_TYPE_COPY        = 5;
     const MESSAGE_TYPE_DELEGATED   = 6;
 
-    protected $_dateTimeFormat = "Ymd\THis\Z";
-
     protected $_xmlBaseElement = 'MeetingRequest';
 
     protected $_properties = array(
diff --git a/lib/kolab_sync_data_email.php b/lib/kolab_sync_data_email.php
--- a/lib/kolab_sync_data_email.php
+++ b/lib/kolab_sync_data_email.php
@@ -406,9 +406,9 @@
             $meeting = array();
 
             $meeting['allDayEvent'] = $event['allday'] ?? null ? 1 : 0;
-            $meeting['startTime'] = $event['start'];
-            $meeting['dtStamp'] = $event['created'] ?? null;
-            $meeting['endTime'] = $event['end'] ?? null;
+            $meeting['startTime'] = self::date_from_kolab($event['start']);
+            $meeting['dtStamp'] = self::date_from_kolab($event['dtstamp'] ?? null);
+            $meeting['endTime'] = self::date_from_kolab($event['end'] ?? null);
             $meeting['location'] = $event['location'] ?? null;
 
             //TODO implement recurrences. We can't detect exceptions like this (don't know how), and the recurrences structure is different from event,