private static Day parseCalendarDay(int dayOfWeek) {
        switch (dayOfWeek) {
            case Calendar.SUNDAY:
                return SUN;
            case Calendar.MONDAY:
                return MON;
            case Calendar.TUESDAY:
                return TUE;
            case Calendar.WEDNESDAY:
                return WED;
            case Calendar.THURSDAY:
                return THU;
            case Calendar.FRIDAY:
                return FRI;
            case Calendar.SATURDAY:
                return SAT;
            default:
                throw new RuntimeException("There is no Day for " + dayOfWeek);
        }
    }