public function cmp($value)
	{
		$ts = sfDateTimeToolkit::getTS($value);
		
		if ($this->ts < $ts)
		{
			// less than
			return -1;
		}
		else if ($this->ts > $ts)
		{
			// greater than
			return 1;
		}
		
		// equal to
		return 0;
	}