public Precision getPrecision() {
		if(year<0)
			return Precision.NONE;
		if(month<0) 
			return Precision.YEAR;
		if(day<0)
			return Precision.MONTH;
		if(hour<0 || minute<0) 
			return Precision.DAY;
		if(second<0)
			return Precision.MINUTE;
		return Precision.SECOND;
	}