@Override
  public void initCalendar() {

    // code copied over from UDFWeekOfYear implementation
    calendar.setFirstDayOfWeek(Calendar.MONDAY);
    calendar.setMinimalDaysInFirstWeek(4);
  }
Expression to get week of year.
Extends {@link VectorUDFTimestampFieldString}
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/VectorUDFWeekOfYearString.java