Add or subtract time from any date

The date calculator adds or subtracts days, weeks, months and years from any starting date. Use it to work out a due date, an expiry date, a contract renewal, a visa expiry, a warranty end date or any date that sits a fixed distance from a known date. All calculations run in your browser; nothing is sent to a server.

How to use this calculator

1. Enter your starting date.
2. Choose the unit to add or subtract: days, weeks, months or years.
3. Enter the number (use a negative value to subtract).
4. The result date is calculated and shown instantly.

Worked example

A 90-day warranty starts on March 1, 2026. Adding 90 days lands on May 30, 2026 — that is the date the warranty expires. A 6-month subscription taken on the same day ends on September 1, 2026. A one-year contract ends on March 1, 2027. Each result is computed with correct month lengths and leap-year handling.

Frequently asked questions

What does the date calculator do?

It adds or subtracts a number of days, weeks, months or years from a starting date to give you a new date. Use it to find a due date, expiry date, renewal date or any date that is a fixed distance from a known date.

Does it handle leap years correctly?

Yes. The calculator uses the Gregorian calendar rules, including leap years. February 29 is included where applicable, and adding a year to February 29 in a leap year lands on February 28 or March 1 of a non-leap year as expected.

How does adding months work when the target month is shorter?

Adding one month to January 31 lands on February 28 (or 29 in a leap year) rather than March 3. The calculator clamps the day to the last valid day of the target month, which is the standard convention for date arithmetic.

Can I subtract days to find a past date?

Yes. Enter a negative number or use the subtract option to count backwards from your start date. This is useful for finding deadlines that count back from a delivery or event date.

Is this calculator free?

Yes. It runs entirely in your browser and costs nothing to use. No sign-up, no watermarks, no data sent to a server.