CODEWITHSUNDEEP
c#datetime
makerofthings7
makerofthings7

Reputation: 61483

There are 52.17 weeks in a year. How do I compute current week in C#?

I am saving data into a circular log with designated byte multiples (dataSlots), and I'm calculating the week number based on the days that pass from a reference date.

 DateTime startDate = DateTime.UtcNow;
 for (int ii = 0; ii < 900; ii++)
 {
    currentDate = startDate + new TimeSpan(7 * ii, 1, 1, 1, 1)
    DateTime globalStartReference = new DateTime(2011, 12, 1, 0, 0, 0, DateTimeKind.Utc);
    var span = currentDate - globalStartReference ;
    int dataSlot = 0;
    dataSlot = (span.Days * 7) / 52;
    Console.WriteLine(dataSlot);
 }

My hope is that dataSlot will be an ever-increasing number based upon the current week, however it isn't. I get duplicate entries (and therefore overwrite my data) on these weeks

11
28
44
60
77
88
109

Why am I getting duplicate weeks and how do I account for this? My guess is that there is a fractional number of weeks in a year...

Upvotes: 0

Views: 428

Answers (3)

DaveE
DaveE

Reputation: 3647

If you're just worried about weeks from baseline, years don't enter into it - it's just 7-day increments.

Otherwise you have year and week-of-year; @BACON's answer is probably right for this. You'll get a bit of overlap - Y2W1 may share the same calendar week as Y1W52. Dunno if you'll just add and make that Week 53 but this gets problematic the longer you go.

Upvotes: 0

Lance U. Matthews
Lance U. Matthews

Reputation: 16612

The Calendar.GetWeekOfYear method may be helpful. It doesn't allow for an arbitrary reference date, however you could adjust for that yourself.

Upvotes: 5

Jared Peless
Jared Peless

Reputation: 1120

Are you trying to get the current week for any given year? It looks like from some pre-defined start date ad infinitum. Using the appropriate calendar, and methods it it, you can get a given week of the year based on a particular date, but not x weeks from any arbitrary date.

Plus you need to account for leap years, partial weeks, etc.

Upvotes: 1

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