XL: Formula to Calculate Number of Days in Month

ID: Q81694

The information in this article applies to:

Microsoft Excel for Windows, versions 3.0, 4.0, 4.0a, 5.0, 5.0c
Microsoft Excel for OS/2, versions 2.20, 2.21, 3.0
Microsoft Excel for the Macintosh, versions 3.0, 4.0, 5.0, 5.0a
Microsoft Excel for Windows 95, versions 7.0, 7.0a
Microsoft Excel 97 for Windows
Microsoft Excel 98 Macintosh Edition

SUMMARY

In Microsoft Excel, you can use the date functions to calculate the number of days in a month. For example, you can use the following formula to return the number of days in a month based on a given starting date


   =DAY(DATE(YEAR(The_Date),MONTH(The_Date)+1,0))

where The_Date is the starting date.

This formula works by finding the "zeroth" day of the month after The_Date. Because there is no "zeroth" day of any month, this date is interpreted as the last day of the month containing The_Date. The DAY function then converts this date into a day number.

Or, to calculate the number of days in a month given the month and year, use the following function


   =DAY(DATE(my_year,my_month+1,1)-1)

where my_month is the month for which you want to return the number of days, and my_year is the year. This function calculates the first day of the next month and subtracts 1, which equals the last day of the current month. The DAY function then gives you the day of the month.

MORE INFORMATION

Microsoft Excel Versions 5.0 and Later

Microsoft provides programming examples for illustration only, without warranty either expressed or implied, including, but not limited to, the implied warranties of merchantability and/or fitness for a particular purpose. This article assumes that you are familiar with the programming language being demonstrated and the tools used to create and debug procedures. Microsoft support professionals can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific needs. If you have limited programming experience, you may want to contact the Microsoft fee-based consulting line at (800) 936-5200. For more information about the support options available from Microsoft, please see the following page on the World Wide Web:

http://www.microsoft.com/support/supportnet/overview/overview.asp

In Microsoft Excel versions 5.0 and later, use the following Visual Basic for Applications procedure:


   Sub Test()
       Dim m As Integer, y As Integer, DaysInMonth As Integer
       ' define variable for number of the month, in this example, November
       m = 11
       ' define variable for the year
       y = 1994
       DaysInMonth = DateSerial(y, m + 1, 1) - DateSerial(y, m, 1)
       MsgBox DaysInMonth
   End Sub

REFERENCES

"Function Reference" version 3.0, pages 44, 46, 156, 251

Additional query words: 5.00a 5.00c 7.00a 97 98 XL98 XL97 XL7 XL5 XL4 XL3

Keywords : xlformula
Version : MACINTOSH:3.0,4.0,5.0,5.0a,98; WINDOWS:3.0,4.0,4.0a,5.0,5.0c,7.0,7.0a,97
Platform : MACINTOSH WINDOWS
Issue type : kbinfo