Get a list of weeks for a year - with dates

Question

I've been racking my brains over this, but it's late on a Friday and I'm going round in circles.

I need to create a list of working weeks for a drop down list, with the week number as the value. So the code would output:

Monday 22nd August - Friday 26th September
Monday 29th August - Friday 2 September
Monday 5th September - Friday 9 September

etc..

For the whole year. Any ideas how I would achieve this?

Thanks.

http://stackoverflow.com/questions/5377851/get-date-range-by-week-number-c — StefanE, Sep 09 '11 at 15:32
possible duplicate of [In .net, knowing the week number how can I get the weekdays date?](http://stackoverflow.com/questions/3854429/in-net-knowing-the-week-number-how-can-i-get-the-weekdays-date) — Binary Worrier, Sep 09 '11 at 15:38
should Monday 22nd August - Friday 26th September, read Monday 22nd August - Friday 26th August? — RichK, Sep 09 '11 at 16:46

spender · Accepted Answer · 2011-09-09T16:15:11.693

31

I think the code below complies with ISO 8601:

var jan1 = new DateTime(DateTime.Today.Year , 1, 1);
//beware different cultures, see other answers
var startOfFirstWeek = jan1.AddDays(1 - (int)(jan1.DayOfWeek));
var weeks=
    Enumerable
        .Range(0,54)
        .Select(i => new {
            weekStart = startOfFirstWeek.AddDays(i * 7)
        })
        .TakeWhile(x => x.weekStart.Year <= jan1.Year)
        .Select(x => new {
            x.weekStart,
            weekFinish=x.weekStart.AddDays(4)
        })
        .SkipWhile(x => x.weekFinish < jan1.AddDays(1) )
        .Select((x,i) => new {
            x.weekStart,
            x.weekFinish,
            weekNum=i+1
        });

edited Sep 09 '11 at 16:15

answered Sep 09 '11 at 15:43

spender

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Sorry for the delay - had to go away for a few days - awesome bit of code, thanks! – DarrylGodden Sep 15 '11 at 09:07
@spender Why do you use "4" in .AddDays(4) and what's purpose of using .SkipWhile(x => x.weekFinish < jan1.AddDays(1) ? – mtkachenko Jan 10 '14 at 12:28
@maxim.tkachenko The AddDays(4) is because he wants monday(6.1.) to friday (10.1) – ruedi Aug 19 '14 at 12:37
1

It doesn't seem to comply to the ISO 8601 standard, it gives me 53 weeks in 2014 when there is 52. The 53rd week is in fact the 1st week of 2015 – David Williams Nov 12 '14 at 13:41
What a marvelous solution ++ – MartinZPetrov May 14 '16 at 10:06

score 3 · Answer 2 · answered Sep 09 '11 at 15:33

3

Bear in mind, that week calculations are done differently in different cultures and there is not a bug if you see week number 53!

using System.Globalization;

CultureInfo cultInfo = CultureInfo.CurrentCulture;
int weekNumNow = cultInfo.Calendar.GetWeekOfYear(DateTime.Now,
                     cultInfo.DateTimeFormat.CalendarWeekRule,
                         cultInfo.DateTimeFormat.FirstDayOfWeek);

answered Sep 09 '11 at 15:33

IrishChieftain

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7
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Doesn't this just get the current week number? I think OP is looking for a list of weeks, i.e. 9/11 - 9/17, etc. – James Johnson Sep 09 '11 at 15:38
Valid point :) The rest is just looping thru weeks of year and populating the DDL items. What I've outlined in my answer though is the "gotcha"... – IrishChieftain Sep 09 '11 at 15:43

score 3 · Answer 3 · answered Sep 09 '11 at 16:12

Just updating what Spender put, because I wanted to make the output of your Datetimes more towards what you wanted.

DateTime jan1 = new DateTime(DateTime.Today.Year, 1, 1);
//beware different cultures, see other answers
DateTime startOfFirstWeek = jan1.AddDays(1 - (int)(jan1.DayOfWeek));
var weeks=
    Enumerable
        .Range(0,54)
        .Select(i => new {
            weekStart = startOfFirstWeek.AddDays(i * 7)
        })
        .TakeWhile(x => x.weekStart.Year <= jan1.Year)
        .Select(x => new {
            x.weekStart,
            weekFinish=x.weekStart.AddDays(4)
        })
        .SkipWhile(x => x.weekFinish.Year < jan1.Year)
        .Select((x,i) => new {
            WeekStart = x.weekStart.ToString("dddd, d, MMMM"),
            WeekFinish = x.weekFinish.ToString("dddd, d, MMMM"),
            weekNum=i+1
        });

The change to correct the formatting to what you wanted is in the last select of the anonymous object.

If you like this version still select senders as the answer, as mine was just an update, but I wasn't sure if a comment with a big code chunk on his was appropriate. — Cubicle.Jockey, Sep 09 '11 at 16:13

score 3 · Answer 4 · edited Apr 03 '20 at 14:33

3

You can use the Week class of the Time Period Library for .NET:

DateTime start = DateTime.Now.Date;
DateTime end = start.AddYears( 1 );
Week week = new Week( start );
while ( week.Start < end )
{
  Console.WriteLine( "week " + week );
  week = week.GetNextWeek();
}

edited Apr 03 '20 at 14:33

mayo

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answered Sep 09 '11 at 16:20

score 0 · Answer 5 · answered Sep 09 '11 at 15:39

You may need to tweak this a bit, but it should get you what you need:

static void Main(string[] args)
    {
        List<DateTime[]> weeks = new List<DateTime[]>();

        DateTime beginDate = new DateTime(2011, 01, 01);
        DateTime endDate = new DateTime(2012, 01, 01);

        DateTime monday = DateTime.Today;
        DateTime friday = DateTime.Today;

        while (beginDate < endDate)
        {
            beginDate = beginDate.AddDays(1);

            if (beginDate.DayOfWeek == DayOfWeek.Monday)
            {
                monday = beginDate;
            }
            else if (beginDate.DayOfWeek == DayOfWeek.Friday)
            {
                friday = beginDate;
            }
            else if (beginDate.DayOfWeek == DayOfWeek.Saturday)
            {
                weeks.Add(new DateTime[] { monday, friday });
            }
        }

        for (int x = 0; x < weeks.Count; x++)
        {
            Console.WriteLine(weeks[x][0].Date.ToShortDateString() + " - " + weeks[x][1].Date.ToShortDateString());
        }

        Console.ReadLine();

    }

Get a list of weeks for a year - with dates

5 Answers5

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