WorldCalcs

Add or Subtract Days Calculator

Add or subtract days, weeks, months, or years from any date.

Reviewed by the WorldCalcs team · Methodology · Last reviewed: June 2026

Resulting date

Friday, July 10, 2026

ISO: 2026-07-10 · Friday

What is an add or subtract date calculator?

This tool adds or subtracts a length of time — days, weeks, months or years — from a starting date and shows the resulting date. It is useful for deadlines, due dates, contract end dates and reminders.

How it works

The calculator counts forward or backward from your start date. Days and weeks are simple counts. For months and years it lands on the same day number in the target month, and if that day does not exist it clamps to the last day of the month. Example: 1 January 2026 plus 90 days is 1 April 2026, and 1 March 2025 minus 1 day is 28 February 2025.

All calculations happen in your browser. Nothing is sent, stored, or tracked.

Results are estimates and may contain errors — for general information only, not professional advice. Always verify before relying on them. Disclaimer

How to use

Choose a starting date, type the amount, pick a unit (days, weeks, months, or years), and select whether to add or subtract. The resulting date — including the weekday — updates instantly.

Day and week math uses exact UTC day counting, so daylight-saving changes can't shift the result. For months and years, if the day doesn't exist in the target month (e.g. January 31 + 1 month), the result is clamped to the last day of that month.

Frequently asked questions

How are months and years handled when the day doesn't exist?+

The result is clamped to the last day of the target month. For example, January 31 + 1 month becomes February 28 (or 29 in a leap year).

Are weekends and holidays skipped?+

No. This calculator counts every calendar day. If you only want working days, use the Business Days Calculator instead.

Can I get a date in the past?+

Yes. Choose Subtract and the calculator will move backward from your start date by the amount you enter.

What happens when the target month is shorter?+

The result clamps to the last valid day. 31 January + 1 month = 28 February (or 29 February in a leap year).

Does it count the start date itself?+

No. Adding 1 day to 1 January gives 2 January; the start date is day zero.

Can I subtract time as well as add it?+

Yes. Use the subtract option (or a negative amount) to go backward in time.

How does it handle leap years?+

Day and week counts cross 29 February automatically, and adding whole years keeps the same date except 29 February, which clamps to 28 February in non-leap years.

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