diff --git a/phpgwapi/inc/class.egw.inc.php b/phpgwapi/inc/class.egw.inc.php
index 503684d001..2561bbc498 100644
--- a/phpgwapi/inc/class.egw.inc.php
+++ b/phpgwapi/inc/class.egw.inc.php
@@ -129,14 +129,20 @@ class egw extends egw_minimal
 
 		// if no server timezone set, use date_default_timezone_get() to determine it once
 		// it fills to log with deprecated warnings under 5.3 otherwise
-		if (empty($GLOBALS['egw_info']['server']['server_timezone']))
+		if (empty($GLOBALS['egw_info']['server']['server_timezone']) ||
+			$GLOBALS['egw_info']['server']['server_timezone'] == 'System/Localtime')	// treat invalid tz like empty!
 		{
-			$config = new config('phpgwapi');
-			$config->read_repository();
-			$config->save_value('server_timezone',
-				$GLOBALS['egw_info']['server']['server_timezone'] = date_default_timezone_get());
-			$config->save_repository();
-			error_log(__METHOD__."() stored server_timezone=".$GLOBALS['egw_info']['server']['server_timezone']);
+			try
+			{
+				$tz = new DateTimeZone(date_default_timezone_get());
+				config::save_value('server_timezone',$GLOBALS['egw_info']['server']['server_timezone'] = $tz->getName(),'phpgwapi');
+				error_log(__METHOD__."() stored server_timezone=".$GLOBALS['egw_info']['server']['server_timezone']);
+			}
+			catch(Exception $e)
+			{
+				// do nothing if new DateTimeZone fails (eg. 'System/Localtime' returned), specially do NOT store it!
+				error_log(__METHOD__."() NO valid 'date.timezone' set in your php.ini!");
+			}
 		}
 		date_default_timezone_set($GLOBALS['egw_info']['server']['server_timezone']);
 
diff --git a/setup/inc/class.setup_process.inc.php b/setup/inc/class.setup_process.inc.php
index 628d668c30..39af398422 100755
--- a/setup/inc/class.setup_process.inc.php
+++ b/setup/inc/class.setup_process.inc.php
@@ -263,9 +263,17 @@ class setup_process
 		{
 			$current_config['system_charset'] = $GLOBALS['egw_setup']->system_charset;
 		}
-		// storing default timezone as system timezone
-		$current_config['system_timezone'] = date_default_timezone_get();
-
+		// storing default timezone as server timezone
+		try
+		{
+			$tz = new DateTimeZone(date_default_timezone_get());
+			$current_config['server_timezone'] = $tz->getName();
+		}
+		catch(Exception $e)
+		{
+			// do nothing if new DateTimeZone fails (eg. 'System/Localtime' returned), specially do NOT store it!
+			error_log(__METHOD__."() NO valid 'date.timezone' set in your php.ini!");
+		}
 		$current_config['install_id'] = md5($_SERVER['HTTP_HOST'].microtime(true).$GLOBALS['egw_setup']->ConfigDomain);
 
 		$current_config['postpone_statistics_submit'] = time() + 2 * 30 * 3600;	// ask user in 2 month from now, when he has something to report