Summary
Add or subtract whole months while clamping end-of-month overflow.
Calculation details
January 31 plus one month becomes February 28 or 29.
Formula
Move the month ordinal, then clamp the day to the destination month length.
Worked example
Worked example
January 31 plus one month is February 28, 2026.
How it works
Enter a start date and whole months to add or subtract. End-of-month dates clamp to the destination month length.
Frequently asked questions
What happens at month ends?
Adding months follows calendar month arithmetic; landing on shorter months can clamp to the last valid day of the month.
Is this the same as adding 30 days?
No. Months vary in length. Prefer add-days when you need a fixed day count.
Can months be negative?
Yes. Negative months move the result earlier.