Date difference calculator — days between two dates
Count days, weeks, months and years between two dates, with or without counting the end date, and switch to business days only in one click.
- Runs in your browser
- Nothing you enter is sent
- Free, no account
Choose both dates to see days, weeks, months and business days between them.
How to count the days between two dates
- Enter the start date and the end date. Order does not matter — reversed dates are swapped for you.
- Decide whether the end date counts. Include end date answers "how many days is this booking"; leaving it off answers "how much time has passed".
- Switch on Business days only to ignore Saturdays and Sundays.
- Turn on Include time of day when you need hours and minutes as well as whole days.
Inclusive or exclusive: the one decision that changes the answer
This is the single most common source of "the calculator is wrong" complaints, and it is almost always a definition problem rather than an arithmetic one. Between 3 June and 5 June there are two days of elapsed time, but three days on the calendar. Both numbers are correct; they answer different questions.
| Question | Setting | 3 June to 5 June |
|---|---|---|
| How long until the deadline? | Exclude end date | 2 days |
| How many nights is the hotel stay? | Exclude end date | 2 nights |
| How many days am I on holiday? | Include end date | 3 days |
| How many days of leave do I book? | Include end date | 3 days |
Contracts and statutes usually specify this explicitly — phrases like "clear days", "inclusive of both dates" or "from and including" are there precisely because the default is ambiguous.
Why months are not 30 days
Calendar months are 28, 29, 30 or 31 days long, so any "months between" figure has to choose a convention. This tool counts whole calendar months from the start date and reports the leftover days separately, which matches how rent, notice periods and subscriptions actually work. It also shows the average-month approximation — total days divided by 30.436875, the mean Gregorian month — clearly labelled, because some financial calculations want exactly that.
The average year figure uses 365.2425 days, the length of the mean Gregorian year once the 4-year, 100-year and 400-year leap rules are averaged out.
Business days here versus the business days calculator
The business-day count on this page removes Saturdays and Sundays only. That is the right answer for most quick questions, but SLAs and legal deadlines usually exclude public holidays too, and some regions do not use a Saturday–Sunday weekend at all. When either applies, use the business days calculator, which lets you set the weekend days and keep your own holiday list.
Accuracy notes
- Leap years follow the full Gregorian rule: divisible by 4, except centuries, except centuries divisible by 400. The year 2000 was a leap year; 1900 and 2100 are not.
- Day counts are done on calendar dates rather than timestamps, so a daylight-saving change inside the range cannot add or lose a day.
- When you include the time of day, hours and minutes are measured in your device's local timezone, so a span that crosses a DST boundary correctly comes out 23 or 25 hours long for that day.
- Dates before 1582 are handled with the proleptic Gregorian calendar, which is what ISO 8601 specifies.
Common uses
- Working out notice periods, probation ends and contract terms.
- Counting days sober, days since a project started, or days until a wedding.
- Checking a 90-day visa window or a 30-day return policy.
- Invoice ageing — how many days past due an unpaid invoice is.
- Pregnancy and medical timelines quoted in weeks plus days.
Questions
Should I include the end date?
Include it when both dates are days you are counting — a hotel stay of 3–5 June is three days. Exclude it when you want elapsed time, which is the usual answer for deadlines, notice periods and interest.
Why is "months" not just days ÷ 30?
Calendar months have 28–31 days, so this tool counts whole calendar months from the start date and then reports the leftover days separately. The days ÷ 30.44 approximation is shown too, clearly labelled as an average.
How are business days counted?
Business days count every day that is not a Saturday or Sunday between the two dates. Public holidays are not included here — use the business days calculator if you need a custom holiday list.
Does it handle dates before 1970 or far in the future?
Yes. Dates from year 1 to year 9999 work, and leap years — including the 100/400-year Gregorian rules — are handled correctly.