diff --git a/phpgwapi/inc/class.egw.inc.php b/phpgwapi/inc/class.egw.inc.php
index 8f7b1156ed..8a2b4e55ee 100644
--- a/phpgwapi/inc/class.egw.inc.php
+++ b/phpgwapi/inc/class.egw.inc.php
@@ -125,6 +125,19 @@ class egw extends egw_minimal
 		}
 		//$GLOBALS['egw_info']['server'] = config::read('phpgwapi'); would unserialize arrays
 
+		// 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']))
+		{
+			$config = new config('phpgwapi');
+			$config->read_repository();
+			$config->save_value('server_timezone',
+				$GLOBALS['egw_info']['server']['server_timezone'] = date_default_timezone_get());
+			$config->save_repository();
+			error_log(__METHOD__."() stored server_timezone=".date_default_timezone_get());
+		}
+		date_default_timezone_set($GLOBALS['egw_info']['server']['server_timezone']);
+		
 		// setup the other subclasses
 		$this->translation    = new translation();
 		$this->common         = new common();
@@ -174,7 +187,12 @@ class egw extends egw_minimal
 		{
 			$this->db->Link_ID->SetCharSet($GLOBALS['egw_info']['server']['system_charset']);
 		}
-
+		// restoring server timezone, to avoid warnings under php5.3
+		if (empty($GLOBALS['egw_info']['server']['server_timezone']))
+		{
+			
+			date_default_timezone_set($GLOBALS['egw_info']['server']['server_timezone']);
+		}
 		register_shutdown_function(array($this, 'shutdown'));
 
 		$this->define_egw_constants();
diff --git a/setup/inc/class.setup_process.inc.php b/setup/inc/class.setup_process.inc.php
index 1e2022dfcb..edb116200d 100755
--- a/setup/inc/class.setup_process.inc.php
+++ b/setup/inc/class.setup_process.inc.php
@@ -228,6 +228,9 @@
 			$current_config['tz_offset'] = $datetime->getbestguess();
 			unset($datetime);
 
+			// storing default timezone as system timezone
+			$current_config['system_timezone'] = date_default_timezone_get();
+
 			// RalfBecker: php.net recommend this for security reasons, it should be our default too
 			$current_config['usecookies'] = 'True';