Days between two dates
Count the days, weeks, months and business days between two dates. Includes the inclusive-versus-exclusive trap that causes off-by-one errors.
Runs in your browser
Business days count weekdays crossed, excluding the end date and taking no account of public holidays.
Inclusive or exclusive
This is the question every date difference has to answer, and the reason two calculators disagree by one.
From 3 August to 10 August:
| Counting | Answer | Means |
|---|---|---|
| Exclusive — days elapsed | 7 | the number of nights, or how long the gap is |
| Inclusive — days involved | 8 | the number of dates in the range, both ends counted |
This page counts elapsed days: the difference is 7, because 7 days pass between the two dates. That is what “how many days between” normally means, and it is what date arithmetic in every programming language gives.
Where it goes wrong is when a rule was written the other way. Hotel stays, hire periods and some contractual notice periods count inclusively — a “7 night” booking spans 8 dates — so check which one a rule means before trusting either number.
Years, months and days
The breakdown is calendar arithmetic, not division. From 15 January 2020 to 7 August 2026 is 6 years, 6 months and 23 days, and the three parts add back up to exactly the target date because each is measured from where the previous one landed.
It is not 2396 ÷ 365. A “month” here is a real calendar month of 28 to 31 days, so:
- The same span of days is a different number of months depending on which months it crossed.
- Adding the parts back in a different order can give a different date. Six months and 23 days from January is not the same as 23 days and six months from January.
Both facts are why date libraries disagree with each other, and why anything legal or financial specifies its own counting convention rather than relying on one.
Business days
The figure here counts weekdays crossed, excluding the end date. From Monday to the following Monday is 5.
Two limits worth stating plainly:
- No public holidays are deducted. Holidays are jurisdictional and move — Lunar New Year, Easter and every substitute day shift year to year — so a generic calculator that claimed to handle them would be wrong for most visitors.
- The working week is assumed to be Monday to Friday. That is not universal.
For a deadline that actually matters, count against the relevant holiday calendar rather than this figure.
Weeks
Reported as whole weeks plus the remaining days, since that is how people hold a span in their head. 100 days is 14 weeks and 2 days.
Note that a year is 52 weeks and 1 day, not 52 weeks — which is why a four-weekly cycle produces thirteen payments a year rather than twelve. See days to weeks.
Leap years and 29 February
The count handles them because it works on calendar dates rather than a fixed year length. 2024 has 366 days, and a span crossing 29 February is one day longer than the same span a year later.
A date of 29 February has no anniversary in a common year. The convention used here — and in most jurisdictions for legal purposes — is that it falls on 1 March.
Timezones and daylight saving
Neither affects the answer. This works in calendar dates, not in instants, so a day is a day even when the clock changed by an hour inside it. Doing the same calculation in milliseconds is where the off-by-one-hour errors come from, and this deliberately does not.
Everything is calculated locally
Both dates and the result stay in your browser. See also date add for the reverse question, and the age calculator for the same arithmetic against a birthday.