public static DateTime offsetWeek(Date date, int offset) {
		return offset(date, DateField.WEEK_OF_YEAR, offset);
	}
public static DateTime offsetWeek ( Date date , int offset ) { return offset ( date , DateField . WEEK_OF_YEAR , offset ) ; }
偏移周

@param date 日期
@param offset 偏移周数，正数向未来偏移，负数向历史偏移
@return 偏移后的日期