Excel formula: Get first day of previous month

Generic formula

=EOMONTH(date,-2)+1

Explanation

To get the first day of the previous month for a given date, you can use a simple formula based on the EOMONTH function.

In the example shown, the formula in cell B5 is:

=EOMONTH(B5,-2)+1

How this formula works

The EOMONTH function returns the last day of a month based on a given date. The 2nd argument is months, which specifies how many months in the future or past to move before returning the last day. By traveling back 2 months, then adding one day, we can calculate the first day of the previous month from any given date.

In the example shown, months is supplied as -2, which causes EOMONTH to return 4/30/2015. Then, 1 day is added to get 5/1/2015.

Author

Dave Bruns

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