Date difference calculator

The off-by-one that starts arguments

From 1 March to 8 March is seven days. It is also eight days. Both are correct, and which one you want depends entirely on what you are counting: seven nights in a hotel, but eight days of car hire; seven days until a deadline, but eight days of a festival that runs from the 1st to the 8th.

This is why two date calculators so often disagree, and why the choice is a visible setting here instead of a convention buried in the code. If a figure from somewhere else is one out from this one, that is almost always the reason.

Working days, and what this cannot know

The working-days figure counts Monday to Friday within the same run of days as the total. It deducts no public holidays, and that is a deliberate limit rather than an omission. There is no universal holiday calendar: they differ by country, by region within a country and by year, and a good many of them move with the Easter or the lunar cycle. A list shipped here would be wrong for most people reading it and would go stale within a year.

The weekend is assumed to be Saturday and Sunday, which is also not universal, much of the Middle East works a Sunday to Thursday week. If either assumption does not fit you, the total days and the weeks breakdown are true everywhere and are the figures to use.

Leap years handle themselves

Both dates are converted to a continuous day number before being subtracted, so every 29 February between them is counted without anything special happening. That also means the century rule comes out right: 1900 was not a leap year and 2000 was, so the hundred years between them are 36,524 days rather than the 36,525 an average of 365.25 would suggest.

Reading the breakdown

The years, months and days figure measures the distance between the two dates, so it does not move when you change the counting option, 1 March to 8 March is a gap of seven days however many days you decide to count. Only the totals shift.

Months in that breakdown are calendar months, not a fixed 30 days, which is why it will not divide neatly into the day count. The day count is the exact figure; everything else is a way of describing it.