diff --git a/calendar/inc/class.calendar_bo.inc.php b/calendar/inc/class.calendar_bo.inc.php
index 33783bddf0..438af26217 100644
--- a/calendar/inc/class.calendar_bo.inc.php
+++ b/calendar/inc/class.calendar_bo.inc.php
@@ -803,11 +803,11 @@ class calendar_bo
 					$time->setTime(23, 59, 59);
 					$event['recur_enddate'] = egw_time::to($time, $date_format);
 				}
-				$timestamps = array('modified','created');
+				$timestamps = array('modified','created','max_user_modified');
 			}
 			else
 			{
-				$timestamps = array('start','end','modified','created','recur_enddate','recurrence');
+				$timestamps = array('start','end','modified','created','recur_enddate','recurrence','max_user_modified');
 			}
 			// we convert here from the server-time timestamps to user-time and (optional) to a different date-format!
 			foreach ($timestamps as $ts)
diff --git a/calendar/inc/class.calendar_so.inc.php b/calendar/inc/class.calendar_so.inc.php
index c5c05a06fd..55773ce34a 100644
--- a/calendar/inc/class.calendar_so.inc.php
+++ b/calendar/inc/class.calendar_so.inc.php
@@ -228,6 +228,7 @@ class calendar_so
 			}
 		}
 
+		$need_max_user_modified = array();
 		// participants, if a recur_date give, we read that recurance, plus the one users from the default entry with recur_date=0
 		// sorting by cal_recur_date ASC makes sure recurence status always overwrites series status
 		foreach($this->db->select($this->user_table,'*',array(
@@ -242,11 +243,23 @@ class calendar_so
 			$events[$row['cal_id']]['participants'][$uid] = $status;
 			$events[$row['cal_id']]['participant_types'][$row['cal_user_type']][$row['cal_user_id']] = $status;
 
-			if (($modified = $this->db->from_timestamp($row['cal_user_modified'])) > $events[$row['cal_id']]['max_user_modified'])
+			if ($events[$row['cal_id']]['recur_type'])
+			{
+				$need_max_user_modified[$row['cal_id']] = $row['cal_id'];
+			}
+			elseif (($modified = $this->db->from_timestamp($row['cal_user_modified'])) > $events[$row['cal_id']]['max_user_modified'])
 			{
 				$events[$row['cal_id']]['max_user_modified'] = $modified;
 			}
 		}
+		// max_user_modified for recurring events has to include all recurrences, above code only querys $recur_date!
+		if ($need_max_user_modified)
+		{
+			foreach($this->max_user_modified($need_max_user_modified) as $id => $modified)
+			{
+				$events[$id]['max_user_modified'] = $modified;
+			}
+		}
 
 		// custom fields
 		foreach($this->db->select($this->extra_table,'*',array('cal_id'=>$ids),__LINE__,__FILE__,false,'','calendar') as $row)
@@ -1582,6 +1595,10 @@ ORDER BY cal_user_type, cal_usre_id
 			'cal_start'  => $start,
 		),__LINE__,__FILE__,'calendar');
 
+		if (!is_array($participants))
+		{
+			error_log(__METHOD__."($cal_id, $start, $end, ".array2string($participants).") participants is NO array! ".function_backtrace());
+		}
 		foreach($participants as $uid => $status)
 		{
 			if ($status == 'G') continue;	// dont save group-invitations