private Thread startVectorManipulationThread(final int vectorLength, final int epochDay) {
    Thread thread = new Thread(() -> {
      DateColumnVector columnVector = new DateColumnVector(vectorLength).setUsingProlepticCalendar(true);
      for (int i = 0; i < vectorLength; i++) {
        columnVector.vector[i] = epochDay;
      }
      columnVector.changeCalendar(false, true);
    });
    thread.start();
    return thread;
  }
Test case for DateColumnVector's changeCalendar
epoch days, hybrid representation, proleptic representation
  16768: hybrid: 2015-11-29 proleptic: 2015-11-29
-141418: hybrid: 1582-10-24 proleptic: 1582-10-24
-141427: hybrid: 1582-10-15 proleptic: 1582-10-15
-141428: hybrid: 1582-10-04 proleptic: 1582-10-14
-141430: hybrid: 1582-10-02 proleptic: 1582-10-12
-141437: hybrid: 1582-09-25 proleptic: 1582-10-05
-141438: hybrid: 1582-09-24 proleptic: 1582-10-04
-499952: hybrid: 0601-03-04 proleptic: 0601-03-07
-499955: hybrid: 0601-03-01 proleptic: 0601-03-04
@throws Exception
storage-api/src/test/org/apache/hadoop/hive/ql/exec/vector/TestDateColumnVector.java