code: private static int dayToUtilDay(int day) {
          switch (day) {
              case EventRecurrence.SU: return Calendar.SUNDAY;
              case EventRecurrence.MO: return Calendar.MONDAY;
              case EventRecurrence.TU: return Calendar.TUESDAY;
              case EventRecurrence.WE: return Calendar.WEDNESDAY;
              case EventRecurrence.TH: return Calendar.THURSDAY;
              case EventRecurrence.FR: return Calendar.FRIDAY;
              case EventRecurrence.SA: return Calendar.SATURDAY;
              default: throw new IllegalArgumentException("bad day argument: " + day);
          }
      }
docs: Converts EventRecurrence's day of week to DateUtil's day of week.
  @param day of week as an EventRecurrence value
  @return day of week as a DateUtil value.