C#: Get the first date of week for specified date

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C#: Get the first date of week for specified date

15-12-2008 by Marek Śliwiński

Post moved to new location:

http://code.mareoblo.pl/2008/12/15/c-get-the-first-date-of-week-for-specified-date/

Posted in C# Snippets | Tagged C# Snippets | 9 Comments

9 Responses

on 13-01-2009 at 00:04 Alex Espinoza

I think using a while is not the best option, this can be done easily just finding the difference:

DayOfWeek selDow = cultureInfo.Calendar.GetDayOfWeek(dayInWeek);

int diff = selDow – firstDay;
return dayInWeek.AddDays(-diff);
on 13-01-2009 at 13:29 Marek Śliwiński

Hi Alex,

Thanks for valuable comment. Sure your proposal looks better also for me so I updated my post.

Greetz

Edit: 2009-03-04
Return to Joel code version (which is the only one correct which I know. Try to test 2009-02-01 date as Joel wrote in his comment below).
on 14-01-2009 at 07:46 Houthakmeister

Thanx for this simple solution.

Greetz,

houthakker
on 06-02-2009 at 08:52 Joel Abrahamsson

Marek,

Please disregard my previous post as the code example was flawed.

I read your post with great interest and was starting to rewrite my own post. I did however recognize the above solution and realized that I had, at the time of writing my post, contemplated using it. The problem is however that in .NET sunday is enumerated as 0 and monday as 1 (as opposed to the ISO standard where monday should be 0). This means that if you do this with the above method:

DateTime date = new DateTime(2009, 2, 1);
CultureInfo culture = new CultureInfo(”sv-SE”);
DateTime firstDate = GetFirstDateOfWeek(date, culture);

firstDate will actually be 2009-02-02 as opposed to the correct 2009-01-26.

I’d love to find another solution than the while-loop but so far it’s the only one I’ve found that has always worked for me :/

Best regards,
/Joel
on 04-03-2009 at 22:04 Marek Śliwiński

Joel,

Thanks for you comment which corrected my post edit in good manner! You are completely right. I tested a lot other solutions from the web forums, blogs etc. and all failed test with 2009-02-01 :)) I try my own to find better solution but I failed ;)

Thank you very much!

Greetings,
Marek
on 28-04-2009 at 06:15 Sarun

I think this will be much easier to find the first date of the week..

DayOfWeek today = DateTime.Now.DayOfWeek;
DateTime firstDate = DateTime.Now.AddDays(-(int)today);

Regrads,
Sarun P.T
Pala
on 28-04-2009 at 13:21 Marek Śliwiński

Sarun,

Actually your piece of code is wrong. Please test it on 2009-02-01 date (1 feburary 2009). Good result should be 2009-01-26 (1st date of week for this test date).

Greetz,
Marek
on 29-07-2009 at 15:18 benoit

I think this is a better answer. Works with 2009-02-01 too.

http://stackoverflow.com/questions/38039/how-can-i-get-the-datetime-for-the-start-of-the-week
on 30-07-2009 at 07:53 Marek Śliwiński

Thanks a lot for sharing this solution! Looks perfect :)