public static function expireCache( $timestamp = false, $locale = null )
    {
        if ( $timestamp === false )
            $timestamp = time();

        $handler = eZExpiryHandler::instance();
        if ( $locale )
            $handler->setTimestamp( self::EXPIRY_KEY . '-' . $locale, $timestamp );
        else
            $handler->setTimestamp( self::EXPIRY_KEY, $timestamp );
        $handler->store();
        self::resetGlobals();
    }