public static DateTime truncate(Date date, DateField dateField) {
		return new DateTime(truncate(calendar(date), dateField));
	}
public static DateTime truncate ( Date date , DateField dateField ) { return new DateTime ( truncate ( calendar ( date ) , dateField ) ) ; }
修改日期为某个时间字段起始时间

@param date {@link Date}
@param dateField 时间字段
@return {@link DateTime}
@since 4.5.7