diff --git a/plugins/calendar/drivers/database/database_driver.php b/plugins/calendar/drivers/database/database_driver.php
index f88ecb3f..2f9dd4bb 100644
--- a/plugins/calendar/drivers/database/database_driver.php
+++ b/plugins/calendar/drivers/database/database_driver.php
@@ -331,15 +331,17 @@ class database_driver extends calendar_driver
             
             // use start date from master but try to be smart on time or duration changes
             $old_start_date = date('Y-m-d', $old['start']);
-            $old_start_time = date('H:i:s', $old['start']);
+            $old_start_time = date('H:i', $old['start']);
             $old_duration = $old['end'] - $old['start'];
             
             $new_start_date = date('Y-m-d', $event['start']);
-            $new_start_time = date('H:i:s', $event['start']);
+            $new_start_time = date('H:i', $event['start']);
             $new_duration = $event['end'] - $event['start'];
             
+            $diff = $old_start_date != $new_start_date || $old_start_time != $new_start_time || $old_duration != $new_duration;
+            
             // shifted or resized
-            if ($old_start_date == $new_start_date || $old_duration == $new_duration) {
+            if ($diff && $event['id'] != $master['id'] && ($old_start_date == $new_start_date || $old_duration == $new_duration)) {
               $event['start'] = $master['start'] + ($event['start'] - $old['start']);
               $event['end'] = $event['start'] + $new_duration;
             }
diff --git a/plugins/calendar/drivers/kolab/kolab_calendar.php b/plugins/calendar/drivers/kolab/kolab_calendar.php
index 3f779bce..a4a88cd8 100644
--- a/plugins/calendar/drivers/kolab/kolab_calendar.php
+++ b/plugins/calendar/drivers/kolab/kolab_calendar.php
@@ -447,10 +447,15 @@ class kolab_calendar
     
     $events = array();
     $duration = $event['end'] - $event['start'];
-    $next = new Horde_Date($event['start']);
+    $tz_offset = $event['allday'] ? $this->cal->timezone * 3600 - date('Z') : 0;
+    $next = new Horde_Date($event['start'] + $tz_offset);  # shift all-day times to server timezone because computation operates in local TZ
     $i = 0;
     while ($next = $recurrence->nextActiveRecurrence(array('year' => $next->year, 'month' => $next->month, 'mday' => $next->mday + 1, 'hour' => $next->hour, 'min' => $next->min, 'sec' => $next->sec))) {
-      $rec_start = $next->timestamp();
+      if ($event['allday']) {
+        $next->hour = $hour;  # fix time for all-day events
+        $next->min = 0;
+      }
+      $rec_start = $next->timestamp() - $tz_offset;
       $rec_end = $rec_start + $duration;
       $rec_id = $event['id'] . '-' . ++$i;
       
diff --git a/plugins/calendar/drivers/kolab/kolab_driver.php b/plugins/calendar/drivers/kolab/kolab_driver.php
index 3e41426a..3d60f826 100644
--- a/plugins/calendar/drivers/kolab/kolab_driver.php
+++ b/plugins/calendar/drivers/kolab/kolab_driver.php
@@ -660,15 +660,17 @@ class kolab_driver extends calendar_driver
 
         // use start date from master but try to be smart on time or duration changes
         $old_start_date = date('Y-m-d', $old['start']);
-        $old_start_time = date('H:i:s', $old['start']);
+        $old_start_time = date('H:i', $old['start']);
         $old_duration = $old['end'] - $old['start'];
         
         $new_start_date = date('Y-m-d', $event['start']);
-        $new_start_time = date('H:i:s', $event['start']);
+        $new_start_time = date('H:i', $event['start']);
         $new_duration = $event['end'] - $event['start'];
         
+        $diff = $old_start_date != $new_start_date || $old_start_time != $new_start_time || $old_duration != $new_duration;
+        
         // shifted or resized
-        if ($old_start_date == $new_start_date || $old_duration == $new_duration) {
+        if ($diff && $event['id'] != $master['id'] && ($old_start_date == $new_start_date || $old_duration == $new_duration)) {
           $event['start'] = $master['start'] + ($event['start'] - $old['start']);
           $event['end'] = $event['start'] + $new_duration;