How to add days to a date
To find a date a set number of days from a starting point, add the days to the start date. Enter a negative number to subtract days and go backward. The calculator handles month lengths and leap years automatically.
A worked example: starting from 15 January and adding 45 days gives 1 March in a common year, because January has 31 days (16 remaining after the 15th) and February contributes the other 29 - or 28 days in a leap year, which shifts the answer to 29 February. This carrying across month boundaries is exactly where manual counting goes wrong, since months run to 28, 29, 30 or 31 days.
Subtracting works the same way in reverse. Entering -90 from 1 June returns 3 March, rolling back through May, April and March.
How to use this calculator
Pick a start date and enter the days to add (or a negative number to subtract). The result is the new date. To count from today specifically, use the days from today calculator.
Typical uses: a 30-day notice period on a contract, a 90-day return window, a 14-day quarantine or curing time, a 28-day repeat prescription, and project deadlines quoted as "within 60 days of signature". In each case, read the wording carefully - most contracts start counting from the day after the trigger event, which is the convention this calculator follows.
If you instead need the gap between two known dates, or a countdown to a future one, the days between dates calculator and the days ago calculator cover those directions.
Frequently asked questions
- How do I add days to a date?
- Add the number of days to the start date, rolling forward across months and years. The calculator does it instantly.
- Can I subtract days?
- Yes. Enter a negative number to go backward from the start date.
- Does it handle leap years?
- Yes, the result uses the real calendar including leap days.
- Is the start date counted?
- No — adding 1 day to a date gives the next day.
- Does it skip weekends and public holidays?
- No - it counts every calendar day, including Saturdays, Sundays and holidays. If you need a business-day deadline, count working days separately, because a 30-day calendar window is only about 21 or 22 working days.