Add or Subtract Days
Add or subtract a number of days from any date to find the resulting date and weekday.
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Pick a start date, enter a number of days and choose Add (+) or Subtract (−), and this calculator shows the resulting date together with its day of the week. It answers questions like "what date is 90 days from today?" or "which day is 45 days before the exam?" without counting squares on a calendar.
How to use it
- Start date: choose it with the date picker.
- Number of days: type a whole number such as 30, 45 or 180. Decimals are rounded to the nearest whole day, so 2.6 counts as 3.
- Operation: Add (+) moves forward in time, Subtract (−) moves back.
- Click Calculate. The result shows the full date with its weekday, written in your browser's date style, plus the offset applied, such as +90 days.
Worked examples
| Start date | Operation | Result |
|---|---|---|
| 1 January 2026 | +90 days | Wednesday, 1 April 2026 |
| 15 March 2026 | −45 days | Thursday, 29 January 2026 |
| 31 January 2026 | +30 days | Monday, 2 March 2026 |
| 1 March 2026 | +90 days | Saturday, 30 May 2026 |
The third row shows why counting by hand goes wrong: February 2026 has only 28 days, so 30 days after 31 January lands on 2 March, not 28 February or 1 March. Month lengths and leap years are handled automatically.
Days are not months
Many rules are written in months rather than days, and the two only sometimes agree. Three months after 1 January is 1 April, which happens to match 90 days. Three months after 1 March is 1 June, but 90 days after 1 March is 30 May. If a contract, policy or bank rule says "three months", count months on a calendar; if it says "90 days", use this calculator.
Counting conventions: is the start day included?
The calculator treats the start date as day zero, which matches the usual meaning of "30 days after 1 June" (1 July). Some rules count the first day as day one, for example "a 7-day course starting Monday", which ends on Sunday, six days later. In that case enter one day fewer. When a deadline really matters, such as a notice period, a return window or a statutory time limit, check how the document defines the count before relying on either reading.
Everyday uses
- Invoice due dates: "net 45" from an invoice dated 1 January 2026 falls on Sunday, 15 February 2026, so you may want to pay on the Friday before.
- Trial and return windows: find the last day to cancel a 14-day or 30-day trial.
- Planning backwards: subtract days from an event, launch or exam date to find when preparation must begin.
- Travel and visas: check where a 30-, 60- or 90-day stay limit ends.
Calendar days only
Weekends and public holidays are counted like any other day. If you need working days, use the Business Days Calculator to count Monday to Friday between two dates. To measure the gap between two known dates instead of adding to one, the Date Difference Calculator does that directly.