Need to calculate date based on year - week - day

Question

How can I calculate the date in C# when I recieve the year, weeknumber and day in week. For example: Year = 2011 Week = 27 day = 6

result should be 2011-7-10

Thanks to all. I solved it based on the wikipedia algorithm.

For the other way around you have this method: http://msdn.microsoft.com/en-us/library/0666bawa.aspx — David Perlman, Jul 12 '11 at 14:11
possible duplicate of [Calculate date from week number](http://stackoverflow.com/questions/662379/calculate-date-from-week-number) — Daniel Hilgarth, Jul 12 '11 at 14:17

score 2 · Answer 1 · answered Jul 12 '11 at 14:40

2

No C# code here (sorry), but assuming that you're talking about ISO week date, you can find a general algorithm that calculates the Gregorian date of an ISO week date in Wikipedia. Hope it helps.

answered Jul 12 '11 at 14:40

kodkod

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InBetween · Answer 2 · 2011-07-12T15:49:14.047

This should work:

 public static DateTime GetDateTime(int year, int week, int day, CultureInfo cultureInfo)
    {
        DateTime firstDayOfYear = new DateTime(year, 1, 1);
        int firstWeek = cultureInfo.Calendar.GetWeekOfYear(firstDayOfYear, cultureInfo.DateTimeFormat.CalendarWeekRule, cultureInfo.DateTimeFormat.FirstDayOfWeek);
        int dayOffSet = day - (int)cultureInfo.DateTimeFormat.FirstDayOfWeek + 1;
        return firstDayOfYear.AddDays((week - (firstWeek + 1)) * 7 + dayOffSet + 1);
    }

I should point out my implementation is not zero based. (so Year=2011, Week=27, day=6) is july 2nd, 2011.

Need to calculate date based on year - week - day

2 Answers2