public boolean add(Date dt, HiveIntervalYearMonth interval, Date result) {
    if (dt == null || interval == null) {
      return false;
    }

    long resultMillis = addMonthsToMillis(dt.toEpochMilli(), interval.getTotalMonths());
    result.setTimeInMillis(resultMillis);
    return true;
  }
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