This article was previously published under Q179545
This article has been archived. It is offered "as is" and will no longer be updated.
If you use the EOMONTH function to return the last day of a month, the function may return the first day of the next month instead.
For example, the EOMONTH function may incorrectly return 3/1/2100 (March 1, 2100) instead of 2/28/2100 (February 28, 2100).
This problem occurs when the date returned by the EOMONTH function meets the following conditions:
The date is in February. -and-
The date is in a century year that is not evenly divisible by 400, for example:
2100, 2200, 2300, 2500, 2600, 2700, 2900, 3000
NOTE: This problem does not occur if the date is in year 1900 or 2000.
Because the EOMONTH function should always return a date at the end of the month, you can modify the formulas so that they subtract one from the date returned by the EOMONTH function if the date is not at the end of the month. This forces the function to return the correct date, for example:
A1: 1/1/2100 A2: =EOMONTH(A1,1)
The formula in cell A2 returns 3/1/2100, an incorrect date. However, if you change the formula
the formula returns the correct date (2/28/2100) even though the date falls in February of a century year that is not evenly divisible by 400.
This is how the formula works:
If the day of the end of the month is 1, recalculate the end of the month, subtract one, and return the date. Otherwise, recalculate the end of the month and return the date.
Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. This problem no longer occurs in Microsoft Excel 2000.
The EOMONTH function, which is included in the Analysis ToolPak, allows you to return the date of the last day in a month. For example, if you want to determine the last day of the month six months from today's date, use the following formula:
If today is 1/13/98, the function returns 7/31/98: the last day of the month six months from today.
The problem described in this article occurs only when the EOMONTH function returns a date in February of a century year that is not a leap year, for example: