Whether you count the first day changes the answer by a full day, and no other date calculator asks. Add public holidays for eight countries, and months worked out by walking the calendar rather than dividing by 30.44, and the figures here differ from most of what you will find elsewhere — on purpose.
Date Difference Calculator
LiveInclusive or exclusive — the question nobody asks
How many days from 1 January to 10 January? Both answers are right, and which one you need depends entirely on what the number is for:
| Method | Answer | Used by |
|---|---|---|
| Exclusive gaps between days | 9 days | Interest calculations, notice periods, ages, almost every online calculator |
| Inclusive both endpoints counted | 10 days | Leave requests, hotel nights, event durations, court deadlines in many jurisdictions |
Weeks, months and calendar days
“How many days between dates” is one question with several answers, and picking the wrong unit is a common source of confusion in project plans and contracts:
| Unit | What it counts | Watch for |
|---|---|---|
| Calendar days | Every day, weekends included | The default here and almost everywhere. What a deadline usually means |
| Working days | Weekdays minus public holidays | What a delivery estimate usually means — and where most plans go wrong |
| Weeks between | Calendar days ÷ 7 | Rarely a whole number. Shown here as both a decimal and whole weeks plus days |
| Months between | Calendar anniversaries | Not days ÷ 30.44. A month is whatever the calendar says it is |
| Date duration | The whole time between dates | How people actually describe a span: “two years and three months” |
A delivery quoted in working days is roughly 40% longer in calendar days — ten working days is a fortnight, and twenty is a month. That conversion is where a schedule quietly slips, because the two numbers get written down interchangeably and only one of them was ever meant.
Working days, and why holidays change everything
Subtracting weekends is easy. Subtracting the right holidays is not, because they differ by country, several move each year, and some fall on a weekend and get moved to the Monday:
| Country | Typical public holidays | Note |
|---|---|---|
| Japan | 14 — the most here | Four fall in Golden Week alone. Several are “happy Monday” rules moved to create long weekends |
| United States | 11 federal | Six are “nth weekday” rules, not fixed dates. States add their own |
| France, Italy, Brazil, Poland | 11 each | Catholic feast days carry much of the count. Several move with Easter |
| United Kingdom | 8 bank holidays | The fewest in western Europe. Scotland and Northern Ireland differ from England and Wales |
| India | 3 national, dozens regional | Only Republic Day, Independence Day and Gandhi Jayanti are nationwide. States observe very different sets |
| Saudi Arabia, UAE, Egypt | 4 to 8 | Islamic holidays follow the lunar calendar, shift about 11 days a year, and are confirmed by moon sighting rather than calculation |
| Australia, Canada | 7 and 10 national | Both add substantial state or provincial holidays this calculator does not include |
Twenty-one countries are built in, covering 187 national holidays in 2026. Every fixed date is stored; every moveable one is computed. Easter comes from the anonymous Gregorian algorithm, which then produces Good Friday, Easter Monday, Ascension, Whit Monday, Corpus Christi and Brazil’s Carnival by offset. The “nth weekday” rules — American Thanksgiving, Japanese Coming of Age Day, Mexican Constitution Day, New Zealand Labour Day — are computed from the weekday pattern rather than tabulated, so they stay correct in any year.
The weekend itself is not universal. Friday and Saturday is the working week’s end in much of the Middle East, and some sectors work six days. The weekend selector above covers the common patterns; for anything binding, use the calendar your contract names rather than a general-purpose one.
Why months are not days divided by 30.44
Most calculators report months by dividing the day count by the average month length. It is fast, and it is wrong in a way that shows immediately:
30 days ÷ 30.44 = 0.99 months — which reads as “not quite a month”
Walking the calendar = 1 month and 1 day — which is what a person means
Walking is the only method that survives leap years, and it has to walk from the original date rather than adding a year at a time. 29 February 2024 to 29 February 2028 is exactly four years; adding one year repeatedly clamps to the 28th on the first step and never recovers the 29th, reporting four years and one day. This calculator anchors every anniversary to the start date for that reason.
| From → To | Divided by 30.44 | Calendar-walked |
|---|---|---|
| 31 Jan 2024 → 1 Mar 2024 | 0.99 months | 1 month, 1 day |
| 31 Jan → 29 Feb 2024 | 0.95 months | 1 month exactly |
| 29 Feb 2024 → 29 Feb 2028 | 48.0 months | 4 years exactly |
| 31 Mar → 30 Apr 2024 | 0.99 months | 1 month exactly |
Leap years
A year is 365.2422 days, so the calendar corrects itself with a rule most people know half of:
| Rule | Leap? | Example |
|---|---|---|
| Divisible by 4 | Yes | 2024, 2028 |
| … unless divisible by 100 | No | 1900, 2100 |
| … unless divisible by 400 | Yes | 2000 was a leap year |
The century exception catches people out. 1900 was not a leap year and 2100 will not be, which is why spreadsheets built before 2000 sometimes disagree with modern ones by a day: an early version of Lotus 1-2-3 treated 1900 as leap, and the bug was kept for compatibility.
Where the law draws the line
Counting conventions are not a matter of taste when a deadline is legal. Different systems settled on different defaults, and the difference is a full day:
| System | Counting | Rule |
|---|---|---|
| US federal courts | Exclusive | Rule 6 of the Federal Rules of Civil Procedure: exclude the day of the event, include the last day. Weekends and holidays are skipped for periods under 11 days |
| EU law | Exclusive | Regulation 1182/71: a period expressed in days starts the day after the event |
| English civil procedure | Exclusive | CPR 2.8: the day of the act is not counted, and a period of five days or fewer excludes weekends and bank holidays |
| Employment leave | Inclusive | Almost universally. A request for Monday to Friday is five days of leave, not four |
| Hotel nights | Exclusive | Check in on the 1st and out on the 10th is nine nights. The bill counts nights, not days |
The pattern is that legal deadlines count exclusively and entitlements count inclusively — which is intuitive once stated, and the source of the confusion until it is. A deadline is a gap you must act within; leave is a set of days you are away.
The calendar itself is not fixed
Date arithmetic assumes a stable calendar, and the Gregorian one has only been universal for a century:
| Change | When | Effect on date arithmetic |
|---|---|---|
| Gregorian adoption | 1582 in Catholic Europe | 10 days were skipped. 4 October was followed by 15 October |
| Britain and colonies | 1752 | 11 days skipped. Dates before September 1752 in British records need care |
| Russia | 1918 | 13 days skipped. The October Revolution happened in November by the modern calendar |
| Greece | 1923 | The last European country to change |
| Leap seconds | 1972 onwards | Adjust clocks, never dates. A day count is unaffected |
This calculator uses the proleptic Gregorian calendar throughout — the modern rules extended backwards, which is what every computer system does. For dates before 1923 in some countries, and before 1752 in Britain, a historical record may use a different calendar entirely and the arithmetic here will not match a contemporary document.
Common mistakes
Frequently asked questions
How many days are between two dates?
It depends whether you count the first day. From 1 to 10 January is nine days counting the gaps between them, and ten counting the days themselves. Exclusive is the usual default and what almost every calculator gives; inclusive is what leave requests, hotel nights and many court deadlines mean. The selector above switches between them.
Does it count public holidays?
Yes, for twenty-one countries across the Americas, Europe, Asia Pacific and the Middle East. Choose one and the working-day count excludes both weekends and that country’s national holidays, with every holiday in the range listed underneath. Regional holidays — German states, Canadian provinces, Scottish bank holidays — are not included, so check a local calendar if those matter.
Why does another calculator give a different answer?
Almost always one of three reasons: it counts exclusively while you meant inclusively, it ignores public holidays in a working-day count, or it reports months by dividing days by 30.44 instead of walking the calendar. The third makes 31 January to 1 March read as 0.99 months rather than 1 month and 1 day.
How many weeks or months are between two dates?
Weeks are calendar days divided by seven, shown both as a decimal and as whole weeks plus the remaining days. Months are counted by calendar anniversaries rather than division, so 15 March to 15 June is exactly three months whatever the day counts of those months happen to be.
What is the difference between calendar days and working days?
Calendar days count every day; working days skip weekends and public holidays. The gap is large enough to break a schedule — ten working days is a fortnight of calendar time, and twenty is roughly a month. A delivery quoted in one and diarised in the other is how a plan slips without anyone noticing.
Can I choose a different weekend?
Yes. Saturday and Sunday is the default, Friday and Saturday covers much of the Middle East, Sunday only suits a six-day week, and you can turn the weekend off entirely for continuous operations.
How are months and years calculated?
By walking the calendar from the start date, not by dividing. Each anniversary is computed from the original date rather than by adding a year at a time — which matters on 29 February, where repeated addition clamps to the 28th and never recovers, reporting four years and a day where four years is correct.
Was 2000 a leap year?
Yes. Years divisible by 4 are leap years, except centuries, except centuries divisible by 400 — and 2000 passes the last test. 1900 was not, and 2100 will not be. Spreadsheets built on the original Lotus 1-2-3 model still treat 1900 as a leap year, which is why very old date arithmetic can be a day out.
Are the Islamic holiday dates exact?
No, and they cannot be. Eid al-Fitr and Eid al-Adha depend on the sighting of the moon and are confirmed only days beforehand, moving about 11 days earlier each year. The dates here are the widely published estimates; treat anything that depends on them as approximate to within a day.
Is my data stored?
No. Everything runs in your browser with no server request, and works offline once the page has loaded. Nothing is written to disk and nothing persists after you close the tab.
Sources
- US Federal Rules of Civil Procedure, Rule 6. Computing and Extending Time. The exclusive-counting rule for federal deadlines, including how weekends and holidays are treated.
- Council Regulation (EEC, Euratom) No 1182/71. Determining the rules applicable to periods, dates and time limits. The EU standard: a period in days begins the day after the event.
- Civil Procedure Rules (England and Wales), Rule 2.8. Time. The equivalent English rule, with the short-period exclusion of weekends and bank holidays.
- ISO 8601:2019. Date and time representations. Defines the YYYY-MM-DD form used throughout this page and the week-numbering rules.
- Dershowitz N, Reingold EM. Calendrical Calculations. Cambridge University Press. The standard reference for calendar conversion and the anonymous Gregorian algorithm used here to compute Easter.
- UK Government, gov.uk/bank-holidays. The published bank holiday dates for England and Wales, Scotland and Northern Ireland.
- US Office of Personnel Management. Federal holidays, including the “nth weekday” rules for Martin Luther King Jr. Day, Presidents’ Day, Memorial Day, Labor Day, Columbus Day and Thanksgiving.
- Japan Cabinet Office. The National Holidays Act, including the “Happy Monday System” that moves four holidays to the nearest Monday, and the substitute-holiday rule for holidays falling on a Sunday.
- Brazil, Law 662/1949 and Law 6802/1980. The federal holiday list, plus the moveable dates tied to Easter — Carnival at 47 days before, Corpus Christi at 60 days after.
- Government of India, Ministry of Personnel. The gazetted holiday list. Only three holidays are nationwide; the rest are state-determined, which is why this calculator includes only the national three.
- Umm al-Qura calendar, Saudi Arabia. The published civil calendar. Eid dates remain subject to moon sighting and are confirmed only days beforehand, which is why the figures here are marked as estimates.
Easter is computed rather than tabulated, using the anonymous Gregorian algorithm; the dates were verified against the published values for 2024 to 2027 before publication. Holiday dates are the commonly observed national ones and exclude regional variations — German states, Canadian provinces and Scottish bank holidays all differ.
Related calculators
See the full list of Date & Time calculators, or try:
- Age Calculator — exact age with Korean and corrected variants
- Business Days Calculator — adding working days to a date
- Add or Subtract Date — a date a given period away
- Day of the Week — which weekday any date fell on
- Time Duration Calculator — hours and minutes rather than days
- Countdown Calculator — time remaining to an event