/**
* delete all sessions that has been timed out
*
* @param int $maxTimeOut The number of seconds for the session's life time
*
* @return SessionService
*/
public static function cleanUp($maxTimeOut)
{
$now = new UDate();
$now->modify('-' . $maxTimeOut . ' second');
return self::deleteByCriteria('`active` = 0 and `updated` < ?', array($now->__toString()));
}