The server clock is set to Central Standard Time. You cannot change the server time.
You can change the time zone within a php script. Here is a sample code:
<?php putenv("TZ=Asia/Jerusalem"); ?>
You can set the timezone in .htaccess as well. Add the line:
SetEnv TZ Asia/Jerusalem
List of timezones is here: http://us.php.net/manual/en/timezones.php