Calendar.GetWeekOfYear(DateTime, CalendarWeekRule, DayOfWeek) Calendar.GetWeekOfYear(DateTime, CalendarWeekRule, DayOfWeek) Calendar.GetWeekOfYear(DateTime, CalendarWeekRule, DayOfWeek) Calendar.GetWeekOfYear(DateTime, CalendarWeekRule, DayOfWeek) Method

Definition

Returns the week of the year that includes the date in the specified DateTime value.

public:
 virtual int GetWeekOfYear(DateTime time, System::Globalization::CalendarWeekRule rule, DayOfWeek firstDayOfWeek);
public virtual int GetWeekOfYear (DateTime time, System.Globalization.CalendarWeekRule rule, DayOfWeek firstDayOfWeek);
abstract member GetWeekOfYear : DateTime * System.Globalization.CalendarWeekRule * DayOfWeek -> int
override this.GetWeekOfYear : DateTime * System.Globalization.CalendarWeekRule * DayOfWeek -> int
Public Overridable Function GetWeekOfYear (time As DateTime, rule As CalendarWeekRule, firstDayOfWeek As DayOfWeek) As Integer
Parameters
time
DateTime DateTime DateTime DateTime

A date and time value.

rule
CalendarWeekRule CalendarWeekRule CalendarWeekRule CalendarWeekRule

An enumeration value that defines a calendar week.

firstDayOfWeek
DayOfWeek DayOfWeek DayOfWeek DayOfWeek

An enumeration value that represents the first day of the week.

Returns

A positive integer that represents the week of the year that includes the date in the time parameter.

Exceptions

time is earlier than MinSupportedDateTime or later than MaxSupportedDateTime.

-or-

firstDayOfWeek is not a valid DayOfWeek value.

-or-

rule is not a valid CalendarWeekRule value.

Examples

The following code example shows how the result of GetWeekOfYear varies depending on the FirstDayOfWeek and the CalendarWeekRule used. If the specified date is the last day of the year, GetWeekOfYear returns the total number of weeks in that year.

using namespace System;
using namespace System::Globalization;
int main()
{
   
   // Gets the Calendar instance associated with a CultureInfo.
   CultureInfo^ myCI = gcnew CultureInfo( "en-US" );
   Calendar^ myCal = myCI->Calendar;
   
   // Gets the DTFI properties required by GetWeekOfYear.
   CalendarWeekRule myCWR = myCI->DateTimeFormat->CalendarWeekRule;
   DayOfWeek myFirstDOW = myCI->DateTimeFormat->FirstDayOfWeek;
   
   // Displays the number of the current week relative to the beginning of the year.
   Console::WriteLine( "The CalendarWeekRule used for the en-US culture is {0}.", myCWR );
   Console::WriteLine( "The FirstDayOfWeek used for the en-US culture is {0}.", myFirstDOW );
   Console::WriteLine( "Therefore, the current week is Week {0} of the current year.", myCal->GetWeekOfYear( DateTime::Now, myCWR, myFirstDOW ) );
   
   // Displays the total number of weeks in the current year.
   DateTime LastDay = System::DateTime( DateTime::Now.Year, 12, 31 );
   Console::WriteLine( "There are {0} weeks in the current year ( {1}).", myCal->GetWeekOfYear( LastDay, myCWR, myFirstDOW ), LastDay.Year );
}

/*
This code produces the following output.  Results vary depending on the system date.

The CalendarWeekRule used for the en-US culture is FirstDay.
The FirstDayOfWeek used for the en-US culture is Sunday.
Therefore, the current week is Week 1 of the current year.
There are 53 weeks in the current year (2001).
*/
using System;
using System.Globalization;


public class SamplesCalendar  {

   public static void Main()  {

      // Gets the Calendar instance associated with a CultureInfo.
      CultureInfo myCI = new CultureInfo("en-US");
      Calendar myCal = myCI.Calendar;

      // Gets the DTFI properties required by GetWeekOfYear.
      CalendarWeekRule myCWR = myCI.DateTimeFormat.CalendarWeekRule;
      DayOfWeek myFirstDOW = myCI.DateTimeFormat.FirstDayOfWeek;

      // Displays the number of the current week relative to the beginning of the year.
      Console.WriteLine( "The CalendarWeekRule used for the en-US culture is {0}.", myCWR );
      Console.WriteLine( "The FirstDayOfWeek used for the en-US culture is {0}.", myFirstDOW );
      Console.WriteLine( "Therefore, the current week is Week {0} of the current year.", myCal.GetWeekOfYear( DateTime.Now, myCWR, myFirstDOW ));

      // Displays the total number of weeks in the current year.
      DateTime LastDay = new System.DateTime( DateTime.Now.Year, 12, 31 );
      Console.WriteLine( "There are {0} weeks in the current year ({1}).", myCal.GetWeekOfYear( LastDay, myCWR, myFirstDOW ), LastDay.Year );

   }

}

/*
This code produces the following output.  Results vary depending on the system date.

The CalendarWeekRule used for the en-US culture is FirstDay.
The FirstDayOfWeek used for the en-US culture is Sunday.
Therefore, the current week is Week 1 of the current year.
There are 53 weeks in the current year (2001).

*/
Imports System
Imports System.Globalization

Public Class SamplesCalendar

   Public Shared Sub Main()
      
      ' Gets the Calendar instance associated with a CultureInfo.
      Dim myCI As New CultureInfo("en-US")
      Dim myCal As Calendar = myCI.Calendar
      
      ' Gets the DTFI properties required by GetWeekOfYear.
      Dim myCWR As CalendarWeekRule = myCI.DateTimeFormat.CalendarWeekRule
      Dim myFirstDOW As DayOfWeek = myCI.DateTimeFormat.FirstDayOfWeek
      
      ' Displays the number of the current week relative to the beginning of the year.
      Console.WriteLine("The CalendarWeekRule used for the en-US culture is {0}.", myCWR)
      Console.WriteLine("The FirstDayOfWeek used for the en-US culture is {0}.", myFirstDOW)
      Console.WriteLine("Therefore, the current week is Week {0} of the current year.", myCal.GetWeekOfYear(DateTime.Now, myCWR, myFirstDOW))
      
      ' Displays the total number of weeks in the current year.
      Dim LastDay = New System.DateTime(DateTime.Now.Year, 12, 31)
      Console.WriteLine("There are {0} weeks in the current year ({1}).", myCal.GetWeekOfYear(LastDay, myCWR, myFirstDOW), LastDay.Year)
   End Sub 'Main 
End Class 'SamplesCalendar


'This code produces the following output.  Results vary depending on the system date.
'
'The CalendarWeekRule used for the en-US culture is FirstDay.
'The FirstDayOfWeek used for the en-US culture is Sunday.
'Therefore, the current week is Week 1 of the current year.
'There are 53 weeks in the current year (2001).

Remarks

This method can be used to determine the number of weeks in the year by setting time to the last day of the year.

The DateTimeFormatInfo object for a particular culture that uses the calendar indicated by the DateTimeFormatInfo.Calendar property includes the following culture-specific values that can be used for the rule and firstDayOfWeek parameters:

The following example uses the current culture's DateTimeFormatInfo object to determine that January 1, 2011 is in the first week of the year in the Gregorian calendar.

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      DateTimeFormatInfo dfi = DateTimeFormatInfo.CurrentInfo;
      DateTime date1 = new DateTime(2011, 1, 1);
      Calendar cal = dfi.Calendar;
      
      Console.WriteLine("{0:d}: Week {1} ({2})", date1, 
                        cal.GetWeekOfYear(date1, dfi.CalendarWeekRule, 
                                          dfi.FirstDayOfWeek),
                        cal.ToString().Substring(cal.ToString().LastIndexOf(".") + 1));       
   }
}
// The example displays the following output:
//       1/1/2011: Week 1 (GregorianCalendar)
Imports System.Globalization

Module Example
   Public Sub Main()
      Dim dfi As DateTimeFormatInfo = DateTimeFormatInfo.CurrentInfo
      Dim date1 As Date = #1/1/2011#
      Dim cal As Calendar = dfi.Calendar
      
      Console.WriteLine("{0:d}: Week {1} ({2})", date1, 
                        cal.GetWeekOfYear(date1, dfi.CalendarWeekRule, 
                                          dfi.FirstDayOfWeek),
                        cal.ToString().Substring(cal.ToString().LastIndexOf(".") + 1))       
   End Sub
End Module
' The example displays the following output:
'       1/1/2011: Week 1 (GregorianCalendar)

For some calendars, a call to the GetWeekOfYear method throws an ArgumentOutOfRangeException for particular combinations of rule and firstDayOfWeek values even if time is greater than the date returned by that calendar's MinSupportedDateTime property. The following table lists the affected calendars, the specific rule values, and the range of the earliest supported time values. The specific minimum DateTime value depends on the value of the firstDayOfWeek parameter.

Calendar CalendarWeekRule value Gregorian date (M/dd/yyyy) Date in calendar (M/dd/yyyy)
ChineseLunisolarCalendar FirstFullWeek 2/19/1901 to 2/25/1901 1/1/1901 to 1/7/1901
ChineseLunisolarCalendar FirstFourDayWeek 2/19/1901 to 2/22/1901 1/01/1901 to 1/04/1901
HebrewCalendar FirstDay 9/17/1583 1/01/5344
HebrewCalendar FirstFullWeek 9/17/1583 to 9/23/1583 1/01/5344 to 1/07/5344
HebrewCalendar FirstFourDayWeek 9/17/1583 to 9/20/1583 1/01/5344 to 1/04/5344
HijriCalendar FirstFullWeek 7/18/0622 to 7/24/0622 1/01/0001 to 1/07/0001
HijriCalendar FirstFourDayWeek 7/18/0622 to 7/21/0622 1/01/0001 to 1/04/0001
JapaneseLunisolarCalendar FirstFullWeek 1/28/1960 to 2/03/1960 1/01/35 to 1/07/0035
JapaneseLunisolarCalendar FirstFourDayWeek 1/28/1960 to 1/31/1960 1/01/0035 to 1/04/0035
JulianCalendar FirstFullWeek 1/01/0001 to 1/05/0001 1/03/0001 to 1/07/0001
JulianCalendar FirstFourDayWeek 1/01/0001 to 1/02/0001 1/03/0001 to 1/04/0001
KoreanLunisolarCalendar FirstFullWeek 2/14/0918 to 2/20/0918 1/01/0918 to 1/07/0918
KoreanLunisolarCalendar FirstFourDayWeek 2/14/0918 to 2/17/0918 1/01/0918 to 1/04/0918
PersianCalendar FirstFullWeek 3/21/0622 to 3/27/0622 1/01/0001 to 1/07/0001
PersianCalendar FirstFourDayWeek 3/21/0622 to 3/24/0622 1/01/0001 to 1/04/0001
TaiwanLunisolarCalendar FirstFullWeek 2/18/1912 to 2/24/1912 1/01/0001 to 1/07/0001
TaiwanLunisolarCalendar FirstFourDayWeek 2/18/1912 to 2/21/1912 1/01/0001 to 1/04/0001
UmAlQuraCalendar FirstFullWeek 4/30/1900 to 5/06/1900 1/01/1318 to 1/07/1318
UmAlQuraCalendar FirstFourDayWeek 4/30/1900 to 5/03/1900 1/01/1318 to 1/04/1318

Applies to

See Also