Question

Need to check if DateTime is in specific range.
I think I need to calculate knowing YEAR first and last date of DST time in this year.

How would I figure “Sunday of week 2 of March” date?

From 1/1/2007 12:00:00 AM to 12/31/9999 12:00:00 AM
  Begins at 2:00 AM on Sunday of week 2 of March
  Ends at 2:00 AM on Sunday of week 1 of November

For example, I need to check if 11/21/2011 is between Sunday of week 2 in March and Sunday of week 1 of November – answer should be NO

If I pass 8/8/2011 – answer should be yes.

Basically, I need to write function to check if my date belongs to daylight savings time. My only idea so far is to write loops to find 2nd week for example.

So, I would loop from Day 1 in March until I hit Sunday second time. Same thing I would loop (increment days by 1) from day 1 of November until I hit Sunday first time.

In another words, I need function to check if input data is in Daylight Savings time period. Time period defined by constraint above.

P.S. I can’t use TimeZoneInfo since it’s in Silverlight
P.P.S I can’t use DateTime.IsDaylightSavingsTime as I don’t have times with kind “local”

Answer 1

I just did this little method, check it and let me know:

    bool IsInDaylightSavingsTime(DateTime date)
    {
        // get second sunday in march
        DateTime _tempDateMar = new DateTime(date.Year, 3, 1);
        int secondSunDayInMar = (8 - (int)_tempDateMar.DayOfWeek) + 7;
        _tempDateMar = new DateTime(date.Year, 3, secondSunDayInMar, 2, 0, 0);

        //get first sunday in november
        DateTime _tempDateNov = new DateTime(date.Year, 11, 1);
        int firstSunDayInNov = (8 - (int)_tempDateNov.DayOfWeek);
        _tempDateNov = new DateTime(date.Year, 11, firstSunDayInNov, 2, 0, 0);

        return (date >= _tempDateMar && date <= _tempDateNov);
    }