Add or subtract days, months or years from a date
Use this to find a due date, a notice period end, a warranty expiry or a date 90 days ago.
How to use this calculator
- Pick the start date.
- Choose add or subtract.
- Enter years, months and days.
- Read the resulting date and its weekday.
Worked examples
Example 1
21 October 2026 plus 3 months and 15 days.
You enter
| Start date | 2026-10-21 |
|---|---|
| Operation | Add |
| Years | 0 |
| Months | 3 |
| Days | 15 |
You get
| Result | Friday, 5 February 2027 |
|---|---|
| Date | 2027-02-05 |
| Days from the start date | 107 |
Example 2
A 90-day period counted back from 31 March 2027.
You enter
| Start date | 2027-03-31 |
|---|---|
| Operation | Subtract |
| Years | 0 |
| Months | 0 |
| Days | 90 |
You get
| Result | Thursday, 31 December 2026 |
|---|---|
| Date | 2026-12-31 |
| Days from the start date | 90 |
How it works
Years and months are applied first, then days. Adding one month to 31 January gives the last day of February, because February has no 31st.
Check how your contract or agency counts days (calendar or working) before relying on the result.
Formula
New date = start date plus years and months (clamped to the month's last day), then plus days.
Common questions
How do I add working days?
Use the working days calculator to count them between two dates.
What about leap years?
They are handled.
Can I add only days?
Set years and months to zero.
Calculators give estimates for learning and planning. They are not financial, tax, legal or medical advice, and results depend entirely on the numbers you enter. Check rates, limits and rules with an official source or a qualified professional before acting.