Date Calculator
Days between dates & add days.
Date Calculator at a glance
Date Calculator is a free online calculator you can use right now to days between dates & add days โ no account, no install and no usage limit. It runs entirely inside your browser, so whatever you enter stays on your own device.
- Price
- Free โ no trial, no paid tier, no watermark
- Sign-up
- Not required
- Where it runs
- In your browser โ nothing is uploaded to a server
- Works on
- Chrome, Safari, Firefox and Edge โ desktop, tablet and phone
- Category
- Calculators
Days between two dates
Add days to a date
About Date Calculator
Count the exact number of days between two dates, or add and subtract a period from a date to find the result.
The first question to settle is whether the calculation is inclusive. The gap between the 1st and the 3rd is two days if you are counting elapsed time, and three if you are counting the days themselves. Both are correct for different purposes: a hotel charges two nights, while a three-day event running from the 1st to the 3rd occupies three calendar days. Deadlines and notice periods usually count elapsed days, but the wording matters and getting it wrong by one day can be consequential.
Adding months is genuinely ambiguous rather than simply tricky, because months have different lengths. One month after 31 January cannot be 31 February, so implementations either clamp to the last valid day โ 28 or 29 February โ or roll over into March. Neither is wrong, but they disagree, and for contract dates and subscription renewals the difference is real. Adding days avoids the ambiguity entirely.
Leap years are handled automatically. The rule is less simple than 'every four years': a year is a leap year if divisible by 4, except centuries, unless divisible by 400. So 1900 was not a leap year and 2000 was. Any date arithmetic spanning late February needs this, which is why doing it by hand is error-prone.
How to use Date Calculator
- Choose whether to count between two dates or add a period to one.
- Enter your dates or the number of days, weeks or months.
- Read the result, noting whether you need an inclusive or exclusive count.
Frequently asked questions
Is the day count inclusive?
It counts elapsed days between the two dates, so the 1st to the 3rd is two days. If you need to count the calendar days themselves โ for a three-day event โ add one.
What happens when I add a month to the 31st?
It is genuinely ambiguous, since not every month has a 31st. Implementations either clamp to the last valid day of the target month or roll into the next. For contracts and renewals this difference matters, so adding days is safer when precision counts.
Are leap years handled?
Yes. A year is a leap year if divisible by 4, except centuries, unless divisible by 400 โ so 1900 was not and 2000 was. Any calculation crossing late February depends on getting this right.
Does this count working days?
The main count is calendar days. Working-day calculations also need weekends excluded and public holidays applied, and holidays vary by country and region โ so always confirm those against the relevant calendar.