How to Use Excel's EOMONTH Function

By eHow Computers Editor

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Excel's EOMONTH function calculates the last day of the month that is a specified number of months before or after a specified date. It is frequently used to determine due dates that occur on the last day of each month.

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Instructions

Difficulty: Moderate

Step1

Learn the syntax of EOMONTH. It is EOMONTH (start_date, months) where start_date is a date and months is a number of months before or after start_date.

Step2

Enter start_date using the DATE function or some other function that returns a date to prevent the problems that can occur when a date is entered as text. EOMONTH will return the #NUM! error value if start_date is not a valid date or if start_date + months is not a valid date.

Step3

Use a positive number for months to represent a future date and a negative number to represent a past date. Months will be truncated if it is not an integer.

Step4

Observe that EOMONTH returns a date as a serial number. Excel stores dates internally as a positive integer representing the number of days beginning with a default date. Windows uses January 1, 1900, as serial number 1 and Excel for the Macintosh uses January 2, 1904, as serial number 1.

Step5

Study some examples of EOMONTH by entering 01/01/2008 as a date in cell A2. Example 1: EOMONTH(A2,1) will return 02/29/2008 because this is the last day of the month that is one month after 01/01/2008. Example 2: EOMONTH(A2,13) will return 02/28/2009. Note that the day of the month changes because February of 2009 has only 28 days.