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. It deliberately does not know about public holidays, because those differ by country, by region within a country, and by year — a single calculator cannot honestly claim to cover them all. If you are counting toward a deadline that falls near Christmas, Easter, a national day, or a local bank holiday, take the number here and subtract the holidays that apply to you. 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.

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. If you need calendar months — for a rental term, a subscription period, or an age in years and months — count them on a calendar rather than 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 rather than 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.

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 — a statutory notice period, a filing deadline, an interest calculation — treat the figure here as a first pass and confirm it against the rules that actually govern your case, which may count weekends differently, may exclude holidays, or may define the starting day in their own way.