public static function clearDate($ts = null)
	{
		// default to now
		if ($ts === null) $ts = sfDateTimeToolkit::now();
		
		list($H, $i, $s, $m, $d, $Y) = sfDateTimeToolkit::breakdown($ts);
		
		return mktime($H, $i, $s, 0, 0, 0);
	}