public long addMonthsToDays(long days, int months) {
    long millis = DateWritableV2.daysToMillis((int) days);
    millis = addMonthsToMillis(millis, months);
    // Convert millis result back to days
    return DateWritableV2.millisToDays(millis);
  }
Perform month arithmetic to millis value using UTC time zone.
@param millis
@param months
@return
ql/src/java/org/apache/hadoop/hive/ql/util/DateTimeMath.java