diff --git a/plugins/libkolab/lib/kolab_format.php b/plugins/libkolab/lib/kolab_format.php
index aa88f69f..9dc8a31a 100644
--- a/plugins/libkolab/lib/kolab_format.php
+++ b/plugins/libkolab/lib/kolab_format.php
@@ -123,7 +123,7 @@ abstract class kolab_format
             if (!$dateonly)
                 $result->setTime($datetime->format('G'), $datetime->format('i'), $datetime->format('s'));
 
-            if ($tz && $tz->getName() == 'UTC')
+            if ($tz && in_array($tz->getName(), array('UTC','GMT','+00:00')))
                 $result->setUTC(true);
             else if ($tz !== false)
                 $result->setTimezone($tz->getName());