protected function _checkDateFormat( $date )
	{
		$regex = '/^[0-9]{4}-[0-1][0-9]-[0-3][0-9] [0-2][0-9]:[0-5][0-9]:[0-5][0-9]$/';

		if( $date !== null && preg_match( $regex, $date ) !== 1 ) {
			throw new MShop_Exception( sprintf( 'Invalid characters in date "%1$s". ISO format "YYYY-MM-DD hh:mm:ss" expected.', $date ) );
		}
	}