Date Duration Calculator
Pick two dates to see how many days apart they are. Both counts are shown at once — with and without the end date — because that single ambiguity is what makes two calculators disagree about the same pair of dates.
- Years, months, days
- —
- Weeks
- —
- Total months
- —
- Working days
- —
- Hours
- —
- Leap days
- —
Working days assume a Saturday-Sunday weekend and no public holidays. For a different weekend or holidays deducted, use the business days calculator.
Runs in your browser. Nothing uploaded.
How to use it
- Pick a start and end date. Both default to something sensible so the tool is never an empty box.
- Read both answers. The left number is the plain difference. The right number counts both dates.
- Check the breakdown for years and months, weeks, working days and leap days.
Inclusive or exclusive: why answers differ
Type “days between dates” into Google and the fifth suggestion is “including start and end date”. That is not a coincidence. It is the question everyone has and almost no tool answers directly.
There are two correct answers to “how many days between 1 August and 5 August”, and which one you want depends entirely on what you are counting:
| You are counting | Method | 1 Aug to 5 Aug |
|---|---|---|
| How long until something | Plain difference | 4 days |
| Days of an event or holiday | Both endpoints included | 5 days |
| Nights in a hotel | Plain difference | 4 nights |
| Days of a notice period | Usually both included | 5 days |
| Days a library book is overdue | Plain difference | 4 days |
The hotel row is the clearest way to remember it. A stay from the 1st to the 5th is four nights and five days. Same dates, two right answers, and they differ by exactly one.
Most calculators pick one silently, or bury the choice in an unticked checkbox. This one shows both, always, so there is nothing to configure and nothing to guess.
How the days between dates are counted
Convert both dates to a day number, subtract, done. The subtlety is in the details.
Everything is computed in UTC. That sounds like an implementation detail and it is not. Do the arithmetic in local time and a day that crosses a daylight saving change is 23 or 25 hours long, not 24. Divide by 24 and you get 0.958 days, which rounds to zero. This is a real and common bug — it is why some calculators return an answer one day out for ranges spanning late March or early November, and only for some users.
Impossible dates are rejected, not corrected. Enter 30 February and this tool tells you it is not a real date. Feed the same string to JavaScript’s built-in date parser and it silently returns 2 March, and every number after that is wrong without any warning.
Common durations
| Period | Days | Weeks | Working days |
|---|---|---|---|
| 1 week | 7 | 1 | 5 |
| 2 weeks | 14 | 2 | 10 |
| 1 month (30 days) | 30 | 4.3 | ~21 |
| 90 days | 90 | 12.9 | ~64 |
| 6 months | ~182 | 26 | ~130 |
| 1 year | 365 | 52.1 | ~261 |
| Leap year | 366 | 52.3 | ~261 |
| 18 months | ~547 | 78.1 | ~391 |
| 2 years | 730 | 104.3 | ~521 |
| 10 years | 3,652 | 521.7 | ~2,609 |
Working-day figures assume a Saturday-Sunday weekend and no public holidays. Deduct roughly 8 to 11 more per year for public holidays, depending on the country.
Worked example
A contract signed on 15 August 2026 with a 90-day payment term.
- 90 days from 15 August 2026 is 13 November 2026, a Friday.
- Enter both dates and the tool confirms 90 days between them, or 91 counting both.
- The breakdown reads 2 months, 29 days — not 3 months, because August and October both have 31 days.
- Working days: 65, counting both ends and before any public holidays.
That last point catches people out. “90 days” and “3 months” are not the same period, and a contract that says one while both parties assume the other is a dispute waiting to happen.
Business days
The result shows a working-day count alongside the calendar days, assuming a Saturday-Sunday weekend and no holidays. That covers most cases.
If your weekend is Friday-Saturday, or Sunday only, or you need public holidays deducted, the business days calculator handles all three and lists exactly which holidays it removed so you can check the number.
Leap years and month ends
A year is a leap year if it divides by 4, except century years, unless they also divide by 400. So 2024 was one, 2000 was one, and 1900 was not. The result tells you how many 29 Februaries fell inside your range.
Month ends are the genuinely ambiguous part. What is the gap from 28 February to 31 March?
| Reading | Answer |
|---|---|
| Plain days | 31 days |
| Months then leftover days | 1 month, 3 days |
Both are correct. This tool counts the most whole months that fit and then the leftover days, which is what date libraries do and what people mean when they say “a month and a bit”. Adding one month to 31 January gives 28 February, because 31 February does not exist — so the month arithmetic clamps to the end of the shorter month.
The calculation was checked against Python’s datetime across 3,003 date pairs and against python-dateutil for the year/month/day breakdown across 2,009 more, including every awkward month-end case.
Doing it elsewhere
| Where | How |
|---|---|
| Excel / Google Sheets | =B1-A1, then format the cell as a number. Otherwise you get a date in 1900. |
| Excel, business days | =NETWORKDAYS(A1,B1) — excludes weekends, takes an optional holiday range. |
| Python | (b - a).days with two date objects. |
| JavaScript | Subtract two dates and divide by 86400000 — but build them with Date.UTC, or daylight saving will bite. |
| SQL | DATEDIFF(day, a, b) in SQL Server, b - a in PostgreSQL. |
All of these give the plain difference. Add 1 if you want both endpoints counted.
Related
The age calculator uses the same engine to answer the same question about a date of birth. The business days calculator handles weekends and public holidays. If your dates come from different countries, the time zone converter will tell you whether a daylight saving change sits between them.
Frequently asked questions
Should I include the start and end date?
It depends what you are counting, which is why this tool shows both numbers. For a duration — how long until a deadline — you want the plain difference. For counting the days of an event or a notice period, you usually want both endpoints included, which is one more. A hotel stay from the 1st to the 5th is 4 nights but 5 days, and that is the same distinction.
How many days are between two dates?
Subtract the earlier date from the later one. This tool does it in UTC, which matters more than it sounds: doing the arithmetic in local time across a daylight saving change gives 23 or 25 hours for a day and can round to the wrong answer. Enter any two dates from 1900 to 2100 and both counts appear straight away.
How do I count only business days?
The result shows a working-day count alongside the calendar days, assuming a Saturday-Sunday weekend and no public holidays. If you need a different weekend or holidays deducted, the business days calculator handles both.
Why do two calculators give different answers for the same dates?
Almost always the inclusive-versus-exclusive question. One counts the gap between the dates, the other counts the days themselves, and the two differ by exactly one. A few tools also handle month ends differently, so 28 February to 31 March comes out as either one month and three days or a plain 31 days depending on what you asked for.
How are leap years handled?
Automatically, and the result tells you how many 29 Februaries fell inside your range. A year is a leap year if it divides by 4, except century years, unless they also divide by 400 — so 2000 was a leap year and 1900 was not.
How do I calculate days between dates in Excel?
Subtract one cell from the other with =B1-A1, then format the result as a number rather than a date, or Excel will show you a date in 1900. For business days use =NETWORKDAYS(A1,B1), which excludes weekends and takes an optional range of holidays. Excel counts the gap, so add 1 if you want both endpoints included.
Last updated: August 15, 2026