FormulaDates
Calculate a due date N months from a start date
Get the last day of a month N months out from any start date — for invoice due dates or renewal dates — without counting days by hand.
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Your formula
=EOMONTH(B2, 1)
Works in both Excel and Google Sheets unless the fine print below says otherwise.
Why it's built this way
- →EOMONTH jumps straight to the last calendar day of the target month, whatever that day is — the 28th, 30th or 31st — which beats adding a fixed number of days that only works for some months.
- →months_out picks which month it lands on: 0 means the end of the current month, a positive number moves forward that many months, and a negative number moves back.
- →Adding 1 to the result gives the first of the FOLLOWING month instead — a common variant when a due date should start the next cycle rather than end this one.
The fine print
- →EOMONTH returns a date serial number; if the cell shows a large integer instead of a date, apply a date number format to it.
- →months_out should be a whole number — a decimal is truncated toward zero rather than rounded.
- →Works identically in Excel and Google Sheets.