protected function normalizeDateValue($time)
	{
		if(is_string($time))
		{
			if(ctype_digit($time) || ($time{0}=='-' && ctype_digit(substr($time, 1))))
				return (int)$time;
			else
				return strtotime($time);
		}
		elseif (class_exists('DateTime', false) && $time instanceof DateTime)
			return $time->getTimestamp();
		else
			return (int)$time;
	}