code: public static int getCalendarDay(final WeekDay weekday) {
          int calendarDay = -1;
          if (SU.getDay().equals(weekday.getDay())) {
              calendarDay = Calendar.SUNDAY;
          }
          else if (MO.getDay().equals(weekday.getDay())) {
              calendarDay = Calendar.MONDAY;
          }
          else if (TU.getDay().equals(weekday.getDay())) {
              calendarDay = Calendar.TUESDAY;
          }
          else if (WE.getDay().equals(weekday.getDay())) {
              calendarDay = Calendar.WEDNESDAY;
          }
          else if (TH.getDay().equals(weekday.getDay())) {
              calendarDay = Calendar.THURSDAY;
          }
          else if (FR.getDay().equals(weekday.getDay())) {
              calendarDay = Calendar.FRIDAY;
          }
          else if (SA.getDay().equals(weekday.getDay())) {
              calendarDay = Calendar.SATURDAY;
          }
          return calendarDay;
      }
docs: Returns the corresponding <code>java.util.Calendar.DAY_OF_WEEK</code>
  constant for the specified <code>WeekDay</code>.
  @param weekday a week day instance
  @return the corresponding <code>java.util.Calendar</code> day