Add or Subtract Days
Date after or before N days
Input
Result
Everything is calculated in your browser. The dates you type are never sent to a server.
How to use
Works out the date a number of days, weeks, months or years before or after another date. Where a month is too short, the rule is explicit and the screen tells you what it did. Dates are never uploaded.
When to use it
- Pinning down a deadline such as "90 days from signing".
- Counting a treatment or dosage schedule in weeks.
- Looking back to find what date "three months ago" was.
How to use it
- Pick the base date; the Today button fills it in.
- Enter the amount and choose the unit — days, weeks, months or years.
- Choose add or subtract and the result appears immediately.
Good to know
- If the target day does not exist in that month, it falls back to the last day of the month, and you are told (31 January + 1 month = 28 February).
- A 29 February base becomes 1 March in common years, which the screen also states.
- A week is seven days, while months and years follow the calendar — "one month" is not always 30 days.
- Weekends and holidays are not skipped; the plain calendar is used.
Frequently asked questions
Why is 31 January plus one month 28 February?
February has no 31st. When the same day number does not exist, the widely used convention is to fall back to the last day of that month. The screen says so, so the number is never misleading on its own.
90 days and three months give different dates.
They are different things. Ninety days is exactly ninety days later; three months is the same day number three calendar months on. Follow whichever wording your contract uses.
Can it add working days?
Not yet — addition follows the plain calendar. For a weekday-only count between two dates, the date difference tool shows it.
Can I add hours?
This tool works in whole days. For hours and minutes, the elapsed time tool handles two date-times.