XL: How to Calculate the Number of Days in a Month


In Microsoft Excel, you can use 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

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

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

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In Microsoft Excel, you can also 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


For more information about functions, click Microsoft Excel Help on the
Help menu, type about using functions to calculate values in the Office Assistant or the Answer Wizard, and then click Search to view the topics returned.

ID d'article : 214313 - Dernière mise à jour : 13 juil. 2009 - Révision : 1