How to use it
- Choose "Date + months" or "Months between two dates".
- Enter the start date.
- Enter the number of months (negative to go back), or the end date.
- Read the result.
Adding months to a date
Enter a start date and a number of months. A negative number goes back in time. The day of the month stays the same: March 15 + 6 months = September 15.
If the target month doesn't have that day, the result moves to the last day of the month, and the calculator tells you:
| Start date | + months | Result |
|---|---|---|
| January 31 | 1 | February 28 (29 in a leap year) |
| March 31 | 1 | April 30 |
| August 31 | 6 | February 28 (29 in a leap year) |
| May 15 | −3 | February 15 |
This is the same convention most banks, leases and contracts use for monthly dates.
Months between two dates
Enter a start and end date to get the number of full months between them plus the remaining days, and the same span in years.
Example: from January 15, 2026 to June 30, 2027 is 17 months and 15 days, or about 1.42 years.
Full months are counted by stepping forward one month at a time from the start date, so a month from January 31 ends on February 28.
Common uses
- Leases and contracts: when does a 12- or 18-month term end?
- Warranties and subscriptions: the end date of a 24-month warranty.
- Pregnancy and baby milestones: how many months old is the baby?
- Loans: how many monthly payments are left until a payoff date?
- Probation periods and notice periods at work.
Months, weeks and days
Months have different lengths (28 to 31 days), so "a month" isn't a fixed number of days. On average, a month is about 30.44 days or 4.35 weeks. If you need an exact number of days, use the date calculator, which can also add days and weeks. For someone's age in years, months and days, use the age calculator.
The month calculator runs in your browser and works with calendar dates, so time zones and daylight saving time don't affect the result.
Month lengths
| Month | Days |
|---|---|
| January, March, May, July, August, October, December | 31 |
| April, June, September, November | 30 |
| February | 28 (29 in leap years) |
The old rhyme "Thirty days hath September, April, June and November" is an easy way to remember it.
Frequently asked questions
What is 6 months from today?
Keep today as the start date and enter 6. The result keeps the same day of the month, or moves to the month's last day if needed.
How do I count the months between two dates?
Choose "Months between two dates" and enter both dates. You get full months plus the remaining days.
What is January 31 plus one month?
February 28, or February 29 in a leap year, because February has no 31st.
Can I subtract months?
Yes. Enter a negative number of months to go back in time.
Last updated: November 12, 2026