public void changeCalendar(boolean useProleptic, boolean updateData) {
    if (useProleptic == usingProlepticCalendar) {
      return;
    }
    usingProlepticCalendar = useProleptic;
    if (updateData) {
      try {
        updateDataAccordingProlepticSetting();
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
  }
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