Why is this date not in the week of the next year? (C# calendar)

Question

I want to calculate the week number of a given date.

DateTime date = Convert.ToDateTime("31.12.2001");

DateTimeFormatInfo dfi = DateTimeFormatInfo.CurrentInfo;
System.Globalization.Calendar cal = dfi.Calendar;

int weekOfYear = cal.GetWeekOfYear(date, CalendarWeekRule.FirstFourDayWeek,  
   dfi.FirstDayOfWeek);

In my DateTimeFormatInfo, the first day of week is a monday. I want to use the four days rule, means a week belongs to a year in which the majority of its days lie. The 31st of December 2001 is a monday and should then be in week 1 of 2002. However, weekOfYear is returned as 53.

Does someone know what´s wrong?

Not a direct duplicate, but there is some good info in the answers. — H H, Jan 31 '12 at 14:13

score 4 · Accepted Answer · answered Jan 31 '12 at 13:50

4

See the documentation for CalendarWeekRule for the exact rules. In short, December 31 will never be week 1, it will be always something like 52/53. The values on the enumeration influence what week will the first days of January have.

answered Jan 31 '12 at 13:50

svick

236,525
50
385
514

See also [System.Globalization.Calendar.GetWeekOfYear() returns odd results](http://stackoverflow.com/q/8808878/41071). – svick Jan 31 '12 at 14:14
This makes no sense. A week should always have 7 days. What weird stuff is MS doing? – AGuyCalledGerald Jan 31 '12 at 14:17

Why is this date not in the week of the next year? (C# calendar)

1 Answers1