CalDavSynchronizer.DDayICalWorkaround.CalendarDataPreprocessor.CalcTransitionStart C# (CSharp) Метод

    private static iCalDateTime CalcTransitionStart(TimeZoneInfo.TransitionTime transition, int year)
    {
      // For non-fixed date rules, get local calendar
      Calendar cal = CultureInfo.CurrentCulture.Calendar;
      // Get first day of week for transition
      // For example, the 3rd week starts no earlier than the 15th of the month
      int startOfWeek = transition.Week * 7 - 6;
      // What day of the week does the month start on?
      int firstDayOfWeek = (int)cal.GetDayOfWeek(new DateTime(year, transition.Month, 1));
      // Determine how much start date has to be adjusted
      int transitionDay;
      int changeDayOfWeek = (int)transition.DayOfWeek;

      if (firstDayOfWeek <= changeDayOfWeek)
        transitionDay = startOfWeek + (changeDayOfWeek - firstDayOfWeek);
      else
        transitionDay = startOfWeek + (7 - firstDayOfWeek + changeDayOfWeek);

      // Adjust for months with no fifth week
      if (transitionDay > cal.GetDaysInMonth(year, transition.Month))
        transitionDay -= 7;

      return new iCalDateTime(new DateTime( year, transition.Month, transitionDay,
                                            transition.TimeOfDay.Hour, transition.TimeOfDay.Minute, transition.TimeOfDay.Second));
    }