/**
  * Change server and default php timezones.
  *
  * @param string $servertimezone timezone to set in $CFG->timezone (not validated)
  * @param string $defaultphptimezone timezone to fake default php timezone (must be valid)
  */
 public static function setTimezone($servertimezone = 'Australia/Perth', $defaultphptimezone = 'Australia/Perth')
 {
     global $CFG;
     $CFG->timezone = $servertimezone;
     core_date::phpunit_override_default_php_timezone($defaultphptimezone);
     core_date::set_default_server_timezone();
 }