Date Calculator
This free date calculator covers the two date questions that come up constantly: how far apart are two dates, and what date is N days from now?
How to use
- Choose a mode: difference between two dates, add days, or subtract days.
- For difference mode, pick the start and end dates — the day count appears immediately.
- For add/subtract mode, pick a start date and enter the number of days; the resulting date and weekday update instantly.
- Enter 0 anywhere to sanity-check the tool: same date gives 0 days and returns the unchanged date.
Frequently asked questions
How are the days between two dates counted?
The result is the exclusive interval from the start date to the end date: the end date itself is not counted. From 2024-01-01 to 2024-01-02 is 1 day; from a date to itself is 0 days. If you want the inclusive calendar count (both endpoints), add 1 to the difference.
What formula is used for the day difference?
Each calendar date is mapped to a continuous day number, and the difference is simply dayNumber(end) − dayNumber(start). Working on day numbers instead of raw timestamps avoids time-zone errors, so the answer is the same no matter where you are.
Are leap years handled when adding days?
Yes. Adding days operates on the real calendar: 2024-02-28 plus 1 day gives 2024-02-29 because 2024 is a leap year, while 2023-02-28 plus 1 day gives 2023-03-01. Crossing months and year boundaries works the same way.
Can I subtract days to find a past date?
Yes — choose the subtract mode and enter the number of days to go back. You can also switch between add and subtract freely; subtracting 30 days is exactly adding −30 days.
Do my dates get uploaded anywhere?
No. All arithmetic runs in your browser on your own device. The dates you enter are never uploaded, stored or logged.
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About this tool
This free date calculator covers the two date questions that come up constantly: how far apart are two dates, and what date is N days from now? In difference mode you pick a start and an end date and immediately get the number of days between them — useful for project timelines, notice periods, warranty windows, visa stays, interest accrual or counting down to a launch. In add and subtract modes you pick a starting date, enter any number of days, and get the resulting calendar date together with its weekday, so you can instantly see whether a deadline lands on a working day. Month lengths, leap years and year boundaries are all handled by real calendar arithmetic: adding one day to 2024-02-28 lands on 2024-02-29, while the same operation in 2023 lands on 2023-03-01. The day count between two dates is measured as the exclusive interval from start to end, meaning the end date itself is not counted — a one-day span is any date to the following day; simply add one to the result if you need both endpoints included. Every calculation happens locally in your browser as you type, with no uploads and no stored data.