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:


Generic formula



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.

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Dave Bruns

Hi - I'm Dave Bruns, and I run Exceljet with my wife, Lisa. Our goal is to help you work faster in Excel. We create short videos, and clear examples of formulas, functions, pivot tables, conditional formatting, and charts.