public void TestFirstDayOfYear()
        {
            RecurrenceRuleDayOfYear rule = "DWY(Mo50)";

            Assert.Equal(1, rule.Multiplier);
            Assert.Equal(TimeInterval.DayOfWeekPerYear, rule.Frequency);
            Assert.Single(rule.WeekDays);

            Assert.Contains(new DayOfWeekSpecified(DayOfWeek.Monday, +50), rule.WeekDays);
        }
        public void TestLastSunday()
        {
            RecurrenceRuleDayOfYear rule = "DWY(Su-1)";

            Assert.Equal(1, rule.Multiplier);
            Assert.Equal(TimeInterval.DayOfWeekPerYear, rule.Frequency);
            Assert.Single(rule.WeekDays);

            Assert.Contains(new DayOfWeekSpecified(DayOfWeek.Sunday, -1), rule.WeekDays);
        }