Add or Subtract Days from a Date

Working out a due date, a payment deadline, the end of a trial or a shipping date all mean adding days to a date - the kind of mental arithmetic that goes wrong around 30- and 31-day months. This tool takes the date, adds the number of days and shows the result in standard form together with its weekday. Negative numbers are accepted and move backwards, so the same box answers “30 days earlier”. The maths works in calendar days and handles leap years correctly.

This tool runs entirely in your browser. No data is sent to any server.

How to use it

1. 1

   Pick the starting date.

2. 2

   Enter the number of days; use a negative value to go backwards (for example -30).

3. 3

   Read the resulting date and weekday in the cards.

Frequently asked questions

Are weekends counted?

Yes, this is plain calendar arithmetic. If you need working days only, subtract holidays separately; the tool has no business-calendar mode.

Do leap years cause problems?

No. Days are added on the real calendar, so 29 February is handled and the result is always a valid date.

Can I add more than a year?

Yes, any number of days works: 365 moves a year ahead, 730 two years. The only limit is the number range of the browser.