This tutorial will teach you how to calculate the first day of the month in Excel and Google Sheets.

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Calculate First Day of the Month

EOMONTH Function

There’s no Excel function to calculate the first day of the month, but the EOMONTH function will calculate the last day of a month.

To find the first day of a month we will calculate the last day of the previous month and add one day.

Here let’s find the last day of the previous month:

=EOMONTH(B3,-1)

Last day of Previous Month

Now let’s add one day to the result:

=EOMONTH(B3,-1)+1

First-day of month EOMONTH

DAY Function

You can also use the DAY Function to find the first day of the month:

=B3 - DAY(B3)+1

First day of month Day

Here the DAY Function returns the day number of a date. By subtracting this from the current date (and adding 1) we arrive at the first day of the month.

Google Sheets Example

These formulas work exactly the same in Google Sheets as in Excel.

First Day of Month Google sheet