How can I get the DateTime for the start of the week

Question

How do I find the start of the week  both Sunday and Monday  knowing just the current time in C    Something like   DateTime Now StartWeek Monday

User · Answer

Here is a combination of a few of the answers. It uses an extension method that allows the culture to be passed in, if one is not passed in, the current culture is used. This will give it max flexibility and re-use.

/// <summary>
/// Gets the date of the first day of the week for the date.
/// </summary>
/// <param name="date">The date to be used</param>
/// <param name="cultureInfo">If none is provided, the current culture is used</param>
/// <returns>The date of the beggining of the week based on the culture specifed</returns>
public static DateTime StartOfWeek(this DateTime date, CultureInfo cultureInfo=null) =>         
             date.AddDays(-1 * (7 + (date.DayOfWeek - (cultureInfo??CultureInfo.CurrentCulture).DateTimeFormat.FirstDayOfWeek)) % 7).Date;

Example Usage:

public static void TestFirstDayOfWeekExtension() {          
        DateTime date = DateTime.Now;
        foreach(System.Globalization.CultureInfo culture in CultureInfo.GetCultures(CultureTypes.UserCustomCulture | CultureTypes.SpecificCultures)) {
            Console.WriteLine($"{culture.EnglishName}: {date.ToShortDateString()} First Day of week: {date.StartOfWeek(culture).ToShortDateString()}");
        }
    }

User · Answer

try with this in c  With this code you can get both first date and last date of a given week Here Sunday is the first day and Saturday is the last day but you can set both day s   according to your culture  DateTime firstDate   GetFirstDateOfWeek DateTime Parse  05 09 2012   Date DayOfWeek Sunday   DateTime lastDate   GetLastDateOfWeek DateTime Parse  05 09 2012   Date  DayOfWeek Saturday    public static DateTime GetFirstDateOfWeek DateTime dayInWeek  DayOfWeek firstDay        DateTime firstDayInWeek   dayInWeek Date      while  firstDayInWeek DayOfWeek    firstDay          firstDayInWeek   firstDayInWeek AddDays -1        return firstDayInWeek    public static DateTime GetLastDateOfWeek DateTime dayInWeek  DayOfWeek firstDay        DateTime lastDayInWeek   dayInWeek Date      while  lastDayInWeek DayOfWeek    firstDay          lastDayInWeek   lastDayInWeek AddDays 1        return lastDayInWeek

User · Answer

Thanks for the examples  I needed to always use the  CurrentCulture  first day of the week and for an array I needed to know the exact Daynumber   so here are my first extensions   public static class DateTimeExtensions         http   stackoverflow com questions 38039 how-can-i-get-the-datetime-for-the-start-of-the-week       http   stackoverflow com questions 1788508 calculate-date-with-monday-as-dayofweek1     public static DateTime StartOfWeek this DateTime dt                  difference in days         int diff    int dt DayOfWeek -  int CultureInfo CurrentCulture DateTimeFormat FirstDayOfWeek    sunday always0  monday always1  etc             As a result we need to have day 0 1 2 3 4 5 6          if  diff  lt  0                        diff    7                    return dt AddDays -1   diff  Date             public static int DayNoOfWeek this DateTime dt                  difference in days         int diff    int dt DayOfWeek -  int CultureInfo CurrentCulture DateTimeFormat FirstDayOfWeek    sunday always0  monday always1  etc             As a result we need to have day 0 1 2 3 4 5 6          if  diff  lt  0                        diff    7                    return diff   1    Make it 1  7

User · Answer

The following method should return the DateTime that you want   Pass in true for Sunday being the first day of the week  false for Monday   private DateTime getStartOfWeek bool useSunday        DateTime now   DateTime Now      int dayOfWeek    int now DayOfWeek       if  useSunday          dayOfWeek--       if dayOfWeek  lt  0          day of week is Sunday and we want to use Monday as the start of the week        Sunday is now the seventh day of the week         dayOfWeek   6             return now AddDays -1    double dayOfWeek

User · Answer

Calculating this way lets you choose which day of the week indicates the start of a new week  in the example I chose Monday    Note that doing this calculation for a day that is a Monday will give the current Monday and not the previous one     Replace with whatever input date you want DateTime inputDate   DateTime Now     For this example  weeks start on Monday int startOfWeek    int DayOfWeek Monday     Calculate the number of days it has been since the start of the week int daysSinceStartOfWeek     int inputDate DayOfWeek   7 - startOfWeek    7   DateTime previousStartOfWeek   inputDate AddDays -daysSinceStartOfWeek

User · Answer

This would give you the preceding Sunday  I think    DateTime t   DateTime Now  t -  new TimeSpan   int  t DayOfWeek  0  0  0

User · Answer

Using Fluent DateTime   var monday   DateTime Now Previous DayOfWeek Monday   var sunday   DateTime Now Previous DayOfWeek Sunday

User · Answer

Let s combine the culture-safe answer and the extension method answer   public static class DateTimeExtensions       public static DateTime StartOfWeek this DateTime dt  DayOfWeek startOfWeek                System Globalization CultureInfo ci   System Threading Thread CurrentThread CurrentCulture          DayOfWeek fdow   ci DateTimeFormat FirstDayOfWeek          return DateTime Today AddDays - DateTime Today DayOfWeek- fdow

User · Answer

This may be a bit of a hack  but you can cast the  DayOfWeek property to an int  it s an enum and since its not had its underlying data type changed it defaults to int  and use that to determine the previous start of the week   It appears the week specified in the DayOfWeek enum starts on Sunday  so if we subtract 1 from this value that ll be equal to how many days the Monday is before the current date  We also need to map the Sunday  0  to equal 7 so given 1 - 7   -6 the Sunday will map to the previous Monday -  DateTime now   DateTime Now  int dayOfWeek    int now DayOfWeek  dayOfWeek   dayOfWeek    0   7   dayOfWeek  DateTime startOfWeek   now AddDays 1 -  int now DayOfWeek     The code for the previous Sunday is simpler as we don t have to make this adjustment -  DateTime now   DateTime Now  int dayOfWeek    int now DayOfWeek  DateTime startOfWeek   now AddDays - int now DayOfWeek

User · Answer

d   DateTime Now              int dayofweek   int  d DayOfWeek              if  dayofweek    0                                d   d AddDays 1 - dayofweek                             else   d   d AddDays -6

User · Answer

Putting it all together  with Globalization and allowing for specifying the first day of the week as part of the call we have  public static DateTime StartOfWeek   this DateTime dt  DayOfWeek  firstDayOfWeek         DayOfWeek fdow       if   firstDayOfWeek HasValue                  fdow   firstDayOfWeek Value            else               System Globalization CultureInfo ci   System Threading Thread CurrentThread CurrentCulture          fdow   ci DateTimeFormat FirstDayOfWeek             int diff   dt DayOfWeek - fdow       if   diff  lt  0                 diff    7             return dt AddDays  -1   diff   Date

User · Answer

Ugly but it at least gives the right dates back   With start of week set by system       public static DateTime FirstDateInWeek this DateTime dt                while  dt DayOfWeek    System Threading Thread CurrentThread CurrentCulture DateTimeFormat FirstDayOfWeek              dt   dt AddDays -1           return dt          Without       public static DateTime FirstDateInWeek this DateTime dt  DayOfWeek weekStartDay                while  dt DayOfWeek    weekStartDay              dt   dt AddDays -1           return dt

User · Answer

Try to create a function which uses recursion  Your DateTime object is an input and function returns a new DateTime object which stands for the beginning of the week        DateTime WeekBeginning DateTime input                do                       if  input DayOfWeek ToString       Monday                   return input              else                 return WeekBeginning input AddDays -1              while  input DayOfWeek ToString       Monday

User · Answer

public static System DateTime getstartweek         System DateTime dt   System DateTime Now      System DayOfWeek dmon   System DayOfWeek Monday      int span   dt DayOfWeek - dmon      dt   dt AddDays -span       return dt

User · Answer

You could use the excellent Umbrella library   using nVentive Umbrella Extensions Calendar  DateTime beginning   DateTime Now BeginningOfWeek      However  they do seem to have stored Monday as the first day of the week  see the property nVentive Umbrella Extensions Calendar DefaultDateTimeCalendarExtensions WeekBeginsOn   so that previous localized solution is a bit better  Unfortunate   Edit  looking closer at the question  it looks like Umbrella might actually work for that too      Or DateTime Now PreviousDay DayOfWeek Monday  DateTime monday   DateTime Now PreviousMonday     DateTime sunday   DateTime Now PreviousSunday      Although it s worth noting that if you ask for the previous Monday on a Monday  it ll give you seven days back  But this is also true if you use BeginningOfWeek  which seems like a bug

User · Answer

using System  using System Globalization   namespace MySpace       public static class DateTimeExtention                  ToDo  Need to provide culturaly neutral versions           public static DateTime GetStartOfWeek this DateTime dt                        DateTime ndt   dt Subtract TimeSpan FromDays  int dt DayOfWeek                return new DateTime ndt Year  ndt Month  ndt Day  0  0  0  0                      public static DateTime GetEndOfWeek this DateTime dt                        DateTime ndt   dt GetStartOfWeek   AddDays 6               return new DateTime ndt Year  ndt Month  ndt Day  23  59  59  999                      public static DateTime GetStartOfWeek this DateTime dt  int year  int week                        DateTime dayInWeek   new DateTime year  1  1  AddDays  week - 1    7               return dayInWeek GetStartOfWeek                       public static DateTime GetEndOfWeek this DateTime dt  int year  int week                        DateTime dayInWeek   new DateTime year  1  1  AddDays  week - 1    7               return dayInWeek GetEndOfWeek

User · Answer

No one seems to have answered this correctly yet  I ll paste my solution here in case anyone needs it  The following code works regardless if first day of the week is a monday or a sunday or something else   public static class DateTimeExtension     public static DateTime GetFirstDayOfThisWeek this DateTime d          CultureInfo ci   System Threading Thread CurrentThread CurrentCulture      var first    int ci DateTimeFormat FirstDayOfWeek      var current    int d DayOfWeek       var result   first  lt   current         d AddDays -1    current - first           d AddDays first - current - 7        return result         class Program     static void Main           System Threading Thread CurrentThread CurrentCulture   CultureInfo GetCultureInfo  en-US        Console WriteLine  Current culture set to en-US        RunTests        Console WriteLine        System Threading Thread CurrentThread CurrentCulture   CultureInfo GetCultureInfo  da-DK        Console WriteLine  Current culture set to da-DK        RunTests        Console ReadLine           static void RunTests           Console WriteLine  Today  1    0    DateTime Today Date GetFirstDayOfThisWeek    DateTime Today Date ToString  yyyy-MM-dd         Console WriteLine  Saturday 2013-03-02   0    new DateTime 2013  3  2  GetFirstDayOfThisWeek         Console WriteLine  Sunday 2013-03-03   0    new DateTime 2013  3  3  GetFirstDayOfThisWeek         Console WriteLine  Monday 2013-03-04   0    new DateTime 2013  3  4  GetFirstDayOfThisWeek

User · Answer

We like one-liners   Get the difference between the current culture s first day of week and the current day then subtract the number of days from the current day  var weekStartDate   DateTime Now AddDays -  int now DayOfWeek -  int DateTimeFormatInfo CurrentInfo FirstDayOfWeek

User · Answer

For Monday  DateTime startAtMonday   DateTime Now AddDays DayOfWeek Monday - DateTime Now DayOfWeek     For Sunday  DateTime startAtSunday   DateTime Now AddDays DayOfWeek Sunday- DateTime Now DayOfWeek

User · Answer

Quickest way I can come up with is   var sunday   DateTime Today AddDays - int DateTime Today DayOfWeek     If you would like any other day of the week to be your start date all you need to do is add the DayOfWeek value to the end  var monday   DateTime Today AddDays - int DateTime Today DayOfWeek    int DayOfWeek Monday    var tuesday   DateTime Today AddDays - int DateTime Today DayOfWeek    int DayOfWeek Tuesday

User · Answer

namespace DateTimeExample               using System           public static class DateTimeExtension                       public static DateTime GetMonday this DateTime time                                if  time DayOfWeek    DayOfWeek Monday                      return GetMonday time AddDays -1      Recursive call                  return time                                   internal class Program                       private static void Main                                 Console WriteLine DateTime Now GetMonday                     Console ReadLine

User · Answer

Same for end of week  in style of  Compile This s answer        public static DateTime EndOfWeek this DateTime dt                int diff   7 -  int dt DayOfWeek           diff   diff    7   0   diff           DateTime eow   dt AddDays diff  Date           return new DateTime eow Year  eow Month  eow Day  23  59  59  999

User · Answer

Modulo in C  works bad for -1mod7   should be 6  c  returns -1  so     oneliner  solution to this will look like this     private static DateTime GetFirstDayOfWeek DateTime date                return date AddDays -   int date DayOfWeek - 1  -  int Math Floor  double   int date DayOfWeek - 1    7    7

User · Answer

A little more verbose and culture-aware   System Globalization CultureInfo ci        System Threading Thread CurrentThread CurrentCulture  DayOfWeek fdow   ci DateTimeFormat FirstDayOfWeek  DayOfWeek today   DateTime Now DayOfWeek  DateTime sow   DateTime Now AddDays - today - fdow   Date

User · Answer

This would give you midnight on the first Sunday of the week   DateTime t   DateTime Now  t -  new TimeSpan   int  t DayOfWeek  t Hour  t Minute  t Second     This gives you the first Monday at midnight   DateTime t   DateTime Now  t -  new TimeSpan   int  t DayOfWeek - 1  t Hour  t Minute  t Second

User · Answer

Did it for Monday but similar logic for Sunday  public static DateTime GetStartOfWeekDate            Get today s date     DateTime today   DateTime Today         Get the value for today  DayOfWeek is an enum with 0 being Sunday  1 Monday  etc     var todayDayOfWeek    int today DayOfWeek       var dateStartOfWeek   today         If today is not Monday  then get the date for Monday     if  todayDayOfWeek    1                   How many days to get back to Monday from today         var daysToStartOfWeek    todayDayOfWeek - 1              Subtract from today s date the number of days to get to Monday         dateStartOfWeek   today AddDays -daysToStartOfWeek              return dateStartOfWeek

User · Answer

Following on from Compile This  Answer  use the following method to obtain the date for any day of the week  public static DateTime GetDayOfWeek DateTime dateTime  DayOfWeek dayOfWeek       var monday   dateTime Date AddDays  7    dateTime DayOfWeek - DayOfWeek Monday    7    -1       var diff   dayOfWeek - DayOfWeek Monday      if  diff    -1             diff   6           return monday AddDays diff

User · Answer

This will return both the beginning of the week and the end of the week dates        private string   GetWeekRange DateTime dateToCheck                string   result   new string 2           TimeSpan duration   new TimeSpan 0  0  0  0     One day          DateTime dateRangeBegin   dateToCheck          DateTime dateRangeEnd   DateTime Today Add duration            dateRangeBegin   dateToCheck AddDays - int dateToCheck DayOfWeek           dateRangeEnd   dateToCheck AddDays 6 -  int dateToCheck DayOfWeek            result 0    dateRangeBegin Date ToString            result 1    dateRangeEnd Date ToString            return result           I have posted the complete code for calculating the begin end of week  month  quarter and year on my blog ZamirsBlog

User · Answer

var now   System DateTime Now   var result   now AddDays -  now DayOfWeek - System Threading Thread CurrentThread CurrentCulture DateTimeFormat FirstDayOfWeek   7    7   Date

User · Answer

Step 1  Create a static class    public static class TIMEE       public static DateTime StartOfWeek this DateTime dt  DayOfWeek startOfWeek                int diff    7    dt DayOfWeek - startOfWeek     7          return dt AddDays -1   diff  Date            public static DateTime EndOfWeek this DateTime dt  DayOfWeek startOfWeek                int diff    7 -  dt DayOfWeek - startOfWeek     7          return dt AddDays 1   diff  Date            Step2  Use this class to get both start and end day of the week   DateTime dt  TIMEE StartOfWeek DateTime Now  DayOfWeek Monday           DateTime dt1   TIMEE EndOfWeek DateTime Now  DayOfWeek Sunday

User · Answer

if you want saturday or sunday or any day of week but not exceeding current week Sat-Sun  I got you covered with this piece of code   public static DateTime GetDateInCurrentWeek this DateTime date  DayOfWeek day        var temp   date      var limit    int date DayOfWeek      var returnDate   DateTime MinValue       if  date DayOfWeek    day  return date       for  int i   limit  i  lt  6  i                  temp   temp AddDays 1            if  day    temp DayOfWeek                        returnDate   temp              break                      if  returnDate    DateTime MinValue                for  int i   limit  i  gt  -1  i                          date   date AddDays -1                if  day    date DayOfWeek                                returnDate   date                  break                                    return returnDate

User · Answer

Use an extension method  They re the answer to everything  you know      public static class DateTimeExtensions       public static DateTime StartOfWeek this DateTime dt  DayOfWeek startOfWeek                int diff    7    dt DayOfWeek - startOfWeek     7          return dt AddDays -1   diff  Date            Which can be used as follows   DateTime dt   DateTime Now StartOfWeek DayOfWeek Monday   DateTime dt   DateTime Now StartOfWeek DayOfWeek Sunday

User · Answer

Tried several but did not solve the issue with a week starting on a Monday  resulting in giving me the coming Monday on a Sunday  So I modified it a bit and got it working with this code   int delta   DayOfWeek Monday - DateTime Now DayOfWeek  DateTime monday   DateTime Now AddDays delta    1   -6   delta   return monday

[c#] How can I get the DateTime for the start of the week?

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