Time Field Rolling function. Rolls (up/down) a single unit of time on the given time field. For example, to roll the current date up by one day, call roll(Calendar::DATE, true). When rolling on the year or Calendar::YEAR field, it will roll the year value in the range between getMinimum(Calendar::YEAR) and the value returned by getMaximum(Calendar::YEAR). When rolling on the month or Calendar::MONTH field, other fields like date might conflict and, need to be changed. For instance, rolling the month up on the date 01/31/96 will result in 02/29/96. Rolling up always means rolling forward in time; e.g., rolling the year up on "100 BC" will result in "99 BC", for Gregorian calendar. When rolling on the hour-in-day or Calendar::HOUR_OF_DAY field, it will roll the hour value in the range between 0 and 23, which is zero-based.
NOTE: Do not use this method -- use roll(EDateFields, int, UErrorCode&) instead.