Date calculator

Working days, and why the count is the argument

Almost every dispute about a date is really a dispute about counting. "Ten working days" from a Monday is a Friday if you count the start day and the following Monday if you do not, and both parties are certain they are right.

This tool counts inclusively — both end dates are in the range — so Monday to Friday is five working days, not four. That matches how people speak and how most notice periods and delivery estimates are written. The headline number above is the elapsed count, which is the other convention, so you can see both and know which one a document means.

The weekend is selectable because a great deal of the world does not take Saturday and Sunday. Saudi Arabia, Qatar and Oman run Sunday to Thursday; the UAE moved to a Monday–Friday week in 2022. Getting that wrong turns a five-day estimate into a seven-day one.

Public holidays are deliberately not included. They differ by country, by province, by year, and several move with the moon. A calculator that quietly assumed a holiday calendar would be wrong for most of the people using it and would give no sign of it.

31 January plus one month

There is no 31 February, so something has to give, and the two available answers are genuinely different dates. Clamping gives 28 February — the last day of the target month. Rolling gives 3 March, because the overflow spills into the next month.

JavaScript's own date handling rolls. That is why so many calculators get month ends subtly wrong without anyone noticing until an invoice is dated three days late. This one clamps, which is what a person means by "a month later" and what most contracts assume.

The same choice shows up in the other direction. Between 31 January and 1 March, a naive breakdown produces "one month and minus two days" — genuinely, that is what the standard borrow arithmetic returns, because one borrow of February's 28 days does not cover a 30-day shortfall. This page counts whole months forward while they still fit and measures the remainder, which cannot produce a negative and gives one month and one day.

Why the arithmetic runs in UTC

Not for tidiness. In any country that changes its clocks, one day of the year is 23 hours long and one is 25. A calculator that subtracts two local timestamps and divides by 86,400,000 therefore returns a fractional number of days twice a year, and rounding it gives an answer one day out.

UTC has no such day. Every date here is turned into a UTC midnight before anything is compared, which makes the day count exact everywhere in the world and on every date, including the changeover days themselves. The time zone converter is the tool for when the clock time itself matters.

This one, or the age calculator?

They answer the same arithmetic for different purposes. Use the age calculator for people: it gives exact age, the Hijri date, and handles the leap-day birthday question. Use this one for paperwork: working days, a settable weekend, adding a notice period, counting down to a deadline.

Questions

How many working days are between two dates?

Count every day in the range and drop the weekend ones. This tool counts both end dates as included, so Monday to Friday is five working days rather than four — which is what the phrase means to a person, and what a notice period or a delivery estimate is usually built on. The weekend is selectable, because much of the Gulf runs Friday and Saturday instead of Saturday and Sunday.

Does it include the end date?

The working-days row does, so Monday to Friday is five. The big number does not — it is the elapsed count. Both are shown because documents use both and rarely say which.

Why do date calculators disagree by a day?

Usually because of whether the end date is counted. "How many days from Monday to Friday" is four if you are measuring elapsed days and five if you are counting the days themselves. This tool reports the elapsed count as the headline number and the inclusive count in the working-days row, so both are visible instead of one being assumed.

Are public holidays counted?

No, deliberately. They vary by country, province and year, and several move with the lunar calendar. Subtract your own.

What does it do with 31 January plus a month?

There is no 31 February, so a choice has to be made. This tool clamps to the last day of the target month and gives 28 February (29 in a leap year), which is what people mean and what most contracts assume. JavaScript's own date arithmetic rolls forward into March instead, which is why a calculator that does not handle this explicitly quietly gets month-end dates wrong.

Does it handle daylight saving?

It sidesteps it. All the arithmetic happens on UTC midnights, which are always exactly 24 hours apart. Calculators that subtract two local timestamps and divide by 86,400,000 lose or gain a day twice a year in any country that changes its clocks, because one day in the span is 23 or 25 hours long.

Is anything sent anywhere?

No. It runs in your browser and makes no network request with your dates.

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All free, all running entirely in your browser. Built by Maxverse Lab, a remote software studio. Every tool.