public String formatDate(int i) {
    return CalendarUtils.formatDate(vector[i], usingProlepticCalendar);
  }
Change the calendar to or from proleptic. If the new and old values of the flag are the same,
nothing is done. useProleptic - set the flag for the proleptic calendar updateData - change the
data to match the new value of the flag.
storage-api/src/java/org/apache/hadoop/hive/ql/exec/vector/DateColumnVector.java