Date Difference Calculator

This calculator answers a question that sounds trivial and turns out not to be: how far apart are two dates? It reports the gap in whole days, converts that figure into weeks, gives approximate months and years, and separately counts how many of those days are Monday through Friday. The two dates are entered as calendar dates, and everything is measured in whole days. There are no hours or minutes involved, so a date pair always produces the same answer no matter what time of day you run the calculation.

The first thing worth settling is what "between" actually means, because two reasonable people count differently. From 1 March to 3 March there are two days of separation, but three days if you include both the first and the last. This is the classic fence post problem: five fence posts in a straight line have only four gaps between them. Neither answer is wrong; they answer different questions. A hotel charges you for nights, which is the gap; a contract that runs "from the 1st to the 3rd inclusive" covers three days. The "Include the end date" option lets you pick which convention you want, and it changes every figure on the page, not just the day count.

The workday figure counts only Saturdays and Sundays as non-working by default. Public holidays differ by country, by region within a country, and by year, so a single calculator cannot honestly claim to cover them all. That is why an optional "Exclude public holidays for" selector sits below the date fields, offering only the handful of country-year combinations this calculator has actually verified against an official or cross-checked source (the FAQ below explains exactly which ones, and why the list is short on purpose). Leave it on "None" and subtract your own holidays by hand, or pick a supported option to see a separate workday count with those holidays already removed. If your date range falls outside what's verified, the calculator says so plainly instead of guessing. The weekday of each date is determined in UTC rather than in your browser's local time zone, which is what stops the count from silently sliding by a day for visitors in the Americas or the Asia-Pacific region.

It is worth knowing how loosely "business day" is defined across the English-speaking world, because a contract rarely says. The United States has eleven federal holidays, but they bind federal agencies and banks, not private employers, so a courier and a court can disagree about whether a given Monday counted. The United Kingdom does not have national public holidays at all: bank holidays are set separately for England and Wales, for Scotland, and for Northern Ireland, and Scotland alone observes 2 January while Northern Ireland adds St Patrick's Day and the Twelfth of July. When a UK bank holiday falls on a weekend, a substitute weekday is granted, which quietly moves a working day out of that week. Australia goes further still and sets most of its holidays state by state. The Monday-to-Friday figure on this page is the common floor under all of those systems, and the honest starting point.

The month and year figures are approximations, and the labels say so on purpose. Months do not have a fixed length: February has 28 or 29 days, and the rest alternate between 30 and 31. This calculator divides the total day count by 30.44, the average month length across a four-year cycle, and by 365.25 for years. That gives a smooth, comparable number, useful when you want to say "about eleven months", but it is not the same as a calendar month count.

The difference shows up in edge cases. From 31 January to 28 February is one calendar month by most people's reckoning, but only 28 days, which this calculator will report as roughly 0.9 months. Going the other way, from 1 January to 1 March is two calendar months but 59 days, or about 1.94 months here. This is exactly what the separate 'exact years / exact months / exact days' figures further up are for: they walk the calendar month by month instead of dividing, so they always match what you would get counting on a physical calendar, at the cost of not being smoothly comparable across different date ranges the way the divided figure is. If you need calendar months for a rental term, a subscription period, or an age in years and months, read those exact figures instead of dividing days. If you need a proportional figure you can compare across different periods, the division used here is the better tool.

The end date has to fall on or after the start date; entering them the other way round produces an error, not a negative number, since a negative day count is far more often a typo than an intention. Very long ranges are handled without trouble: several centuries between the two dates will still return an answer quickly, because the workday count folds whole seven-day blocks into a single multiplication (any seven consecutive days contain exactly five weekdays) and only walks through the leftover days. One historical caveat applies at that scale: dates before the Gregorian calendar reform of 1582 are computed using today's calendar rules projected backwards, which will not match dates as they were written at the time.

Legal drafting has its own vocabulary for the counting problem this calculator solves, and the phrase to watch for is "clear days". In the English civil procedure rules a period expressed in clear days excludes both the day the period starts and the day it ends, which is one day shorter than the inclusive count and one day shorter again than most people's instinct. Statutory notice periods work differently once more: in the United Kingdom the statutory minimum notice an employer must give is measured in weeks and grows with length of service, while in the United States most notice periods are set by contract and read as calendar days unless the contract says otherwise. Reading which convention a document uses before you count is worth more than any refinement of the count itself.

Everyday uses for this are mostly practical: how many days are left before a deadline, how long a project has been running, how much notice a contract requires, how many working days remain in a quarter, how many days until a trip or an anniversary. For anything with legal or financial consequences, such as a statutory notice period, a filing deadline or an interest calculation, treat the figure here as a first pass and confirm it against the rules that actually govern your case. Those rules may count weekends differently, may exclude holidays, or may define the starting day in their own way.

The quickest way to use the page well is to decide two things before you read a number. First, whether both end dates belong inside the period or only the gap between them does, which the include-the-end-date switch settles. Second, whether you need a calendar figure or a comparable one: the exact years, months and days match a wall calendar, while the approximate months and years are for putting two unequal periods side by side. Once those two choices are made, every line on the page answers the same question consistently, and the number you copy into a form is the one you meant.