DateTime.DaysInMonth(Int32, Int32) Method

Reference

Definition

Namespace:: System

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: DateTime.cs

Source:: DateTime.cs

Source:: DateTime.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Returns the number of days in the specified month and year.

public:
 static int DaysInMonth(int year, int month);

public static int DaysInMonth (int year, int month);

static member DaysInMonth : int * int -> int

Public Shared Function DaysInMonth (year As Integer, month As Integer) As Integer

Parameters

year: Int32

The year.

month: Int32

The month (a number ranging from 1 to 12).

Returns

Int32

The number of days in month for the specified year.

For example, if month equals 2 for February, the return value is 28 or 29 depending upon whether year is a leap year.

Exceptions

ArgumentOutOfRangeException

month is less than 1 or greater than 12.

-or-

year is less than 1 or greater than 9999.

Examples

The following example demonstrates how to use the DaysInMonth method to determine the number of days in July 2001, February 1998 (a non-leap year), and February 1996 (a leap year).

using namespace System;

int main()
{
   const int July = 7;
   const int Feb = 2;
   
   int daysInJuly = System::DateTime::DaysInMonth( 2001, July );
   Console::WriteLine(daysInJuly);   
   // daysInFeb gets 28 because the year 1998 was not a leap year.
   int daysInFeb = System::DateTime::DaysInMonth( 1998, Feb );
   Console::WriteLine(daysInFeb);
   // daysInFebLeap gets 29 because the year 1996 was a leap year.
   int daysInFebLeap = System::DateTime::DaysInMonth( 1996, Feb );
   Console::WriteLine(daysInFebLeap);
}
// The example displays the following output:
//       31
//       28
//       29

open System

let July = 7
let Feb = 2

let daysInJuly = DateTime.DaysInMonth(2001, July)
printfn $"{daysInJuly}"

// daysInFeb gets 28 because the year 1998 was not a leap year.
let daysInFeb = DateTime.DaysInMonth(1998, Feb)
printfn $"{daysInFeb}"

// daysInFebLeap gets 29 because the year 1996 was a leap year.
let daysInFebLeap = DateTime.DaysInMonth(1996, Feb)
printfn $"{daysInFebLeap}"

// The example displays the following output:
//       31
//       28
//       29

using System;

class Example
{
    static void Main()
    {
        const int July = 7;
        const int Feb = 2;

        int daysInJuly = System.DateTime.DaysInMonth(2001, July);
        Console.WriteLine(daysInJuly);

        // daysInFeb gets 28 because the year 1998 was not a leap year.
        int daysInFeb = System.DateTime.DaysInMonth(1998, Feb);
        Console.WriteLine(daysInFeb);

        // daysInFebLeap gets 29 because the year 1996 was a leap year.
        int daysInFebLeap = System.DateTime.DaysInMonth(1996, Feb);
        Console.WriteLine(daysInFebLeap);
    }
}
// The example displays the following output:
//       31
//       28
//       29

Class Example
   Public Shared Sub Main()
      Const July As Integer = 7
      Const Feb As Integer = 2

      Dim daysInJuly As Integer = System.DateTime.DaysInMonth(2001, July)
      Console.WriteLine(daysInJuly)
      
      ' daysInFeb gets 28 because the year 1998 was not a leap year.
      Dim daysInFeb As Integer = System.DateTime.DaysInMonth(1998, Feb)
      Console.WriteLine(daysInFeb)
      ' daysInFebLeap gets 29 because the year 1996 was a leap year.
      Dim daysInFebLeap As Integer = System.DateTime.DaysInMonth(1996, Feb)
      Console.WriteLine(daysInFebLeap)
   End Sub
End Class
' The example displays the following output:
'       31
'       28
'       29

The following example displays the number of days in each month of a year specified in an integer array.

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      int[] years = { 2012, 2014 };
      DateTimeFormatInfo dtfi = DateTimeFormatInfo.CurrentInfo;
      Console.WriteLine("Days in the Month for the {0} culture " +
                        "using the {1} calendar\n",
                        CultureInfo.CurrentCulture.Name,
                        dtfi.Calendar.GetType().Name.Replace("Calendar", ""));
      Console.WriteLine("{0,-10}{1,-15}{2,4}\n", "Year", "Month", "Days");

      foreach (var year in years) {
         for (int ctr = 0; ctr <= dtfi.MonthNames.Length - 1; ctr++) {
            if (String.IsNullOrEmpty(dtfi.MonthNames[ctr]))
               continue;

            Console.WriteLine("{0,-10}{1,-15}{2,4}", year,
                              dtfi.MonthNames[ctr],
                              DateTime.DaysInMonth(year, ctr + 1));
         }
         Console.WriteLine();
      }
   }
}
// The example displays the following output:
//    Days in the Month for the en-US culture using the Gregorian calendar
//
//    Year      Month          Days
//
//    2012      January          31
//    2012      February         29
//    2012      March            31
//    2012      April            30
//    2012      May              31
//    2012      June             30
//    2012      July             31
//    2012      August           31
//    2012      September        30
//    2012      October          31
//    2012      November         30
//    2012      December         31
//
//    2014      January          31
//    2014      February         28
//    2014      March            31
//    2014      April            30
//    2014      May              31
//    2014      June             30
//    2014      July             31
//    2014      August           31
//    2014      September        30
//    2014      October          31
//    2014      November         30
//    2014      December         31

open System
open System.Globalization

let years = [| 2012; 2014 |]
let dtfi = DateTimeFormatInfo.CurrentInfo
printfn $"""Days in the Month for the {CultureInfo.CurrentCulture.Name} culture using the {dtfi.Calendar.GetType().Name.Replace("Calendar", "")} calendar\n"""
printfn $"""{"Year",-10}{"Month",-15}{"Days",4}\n"""

for year in years do
    for i = 0 to dtfi.MonthNames.Length - 1 do
        if not (String.IsNullOrEmpty dtfi.MonthNames[i]) then
            printfn $"{year,-10}{dtfi.MonthNames[i],-15}{DateTime.DaysInMonth(year, i + 1),4}"
    printfn ""

// The example displays the following output:
//    Days in the Month for the en-US culture using the Gregorian calendar
//
//    Year      Month          Days
//
//    2012      January          31
//    2012      February         29
//    2012      March            31
//    2012      April            30
//    2012      May              31
//    2012      June             30
//    2012      July             31
//    2012      August           31
//    2012      September        30
//    2012      October          31
//    2012      November         30
//    2012      December         31
//
//    2014      January          31
//    2014      February         28
//    2014      March            31
//    2014      April            30
//    2014      May              31
//    2014      June             30
//    2014      July             31
//    2014      August           31
//    2014      September        30
//    2014      October          31
//    2014      November         30
//    2014      December         31

Imports System.Globalization

Module Example
   Public Sub Main()
      Dim years() As Integer = { 2012, 2014 }
      Dim dtfi As DateTimeFormatInfo = DateTimeFormatInfo.CurrentInfo
      Console.WriteLine("Days in the Month for the {0} culture " +
                        "using the {1} calendar", 
                        CultureInfo.CurrentCulture.Name, 
                        dtfi.Calendar.GetType.Name.Replace("Calendar", ""))
      Console.WriteLine()
      Console.WriteLine("{0,-10}{1,-15}{2,4}", "Year", "Month", "Days")
      Console.WriteLine()
      
      For Each [year] As Integer In years
         For ctr As Integer = 0 To dtfi.MonthNames.Length - 1
            If String.IsNullOrEmpty(dtfi.MonthNames(ctr)) Then 
               Continue For
            End If    
            
            Console.WriteLine("{0,-10}{1,-15}{2,4}", [year], 
                              dtfi.MonthNames(ctr), 
                              DateTime.DaysInMonth([year], ctr + 1))
         Next
         Console.WriteLine() 
      Next
   End Sub
End Module
' The example displays the following output:
'    Days in the Month for the en-US culture using the Gregorian calendar
'    
'    Year      Month          Days
'    
'    2012      January          31
'    2012      February         29
'    2012      March            31
'    2012      April            30
'    2012      May              31
'    2012      June             30
'    2012      July             31
'    2012      August           31
'    2012      September        30
'    2012      October          31
'    2012      November         30
'    2012      December         31
'    
'    2014      January          31
'    2014      February         28
'    2014      March            31
'    2014      April            30
'    2014      May              31
'    2014      June             30
'    2014      July             31
'    2014      August           31
'    2014      September        30
'    2014      October          31
'    2014      November         30
'    2014      December         31

Remarks

The DaysInMonth method always interprets month and year as the month and year of the Gregorian calendar even if the Gregorian calendar is not the current culture's current calendar. To get the number of days in a specified month of a particular calendar, call that calendar's GetDaysInMonth method.

Applies to

Jaa