Date Difference Calculator
Two dates in, every useful measure of the gap out — including the inclusive and exclusive counts, which differ by one and cause endless confusion.
Inclusive versus exclusive counting
This is the single biggest source of off-by-one errors with dates, and both answers are legitimate — they answer different questions.
From 1 January to 3 January is 2 days later (exclusive), but covers 3 days (inclusive). A hotel stay of three nights spans four calendar days. A project running Monday to Friday is five working days, not four.
Contracts, notice periods and statutory deadlines usually specify which convention applies, and the difference of one day can matter a great deal. When in doubt, count the days out loud.
Why 'months between' is ambiguous
Days are unambiguous; months are not. From 31 January to 28 February is one month by the common convention, but 31 days. From 1 March to 1 April is also one month, and 31 days. From 1 February to 1 March is one month and 28 days.
This is why financial and legal calculations that need precision use day counts rather than month counts, and why several different day-count conventions exist in finance — 30/360, actual/360, actual/365 and actual/actual — each making different assumptions to get around exactly this problem. Our decomposition into years, months and days follows the everyday convention, and the total days figure is the one to use where precision matters.
Working days
The working days figure counts Monday to Friday between the two dates, excluding the end date. It does not account for public holidays, which vary by country and by region, nor for organisations that work Saturdays or observe a Friday–Saturday weekend.
As a rough guide, a typical year contains about 261 weekdays, from which most countries subtract 8 to 14 public holidays, leaving roughly 250 working days. If you need holiday-adjusted figures, take the working days from this calculator and subtract the holidays that fall in the range.
Frequently asked questions
Why does the calculator use UTC?
To avoid daylight saving transitions producing a spurious extra hour that rounds into a whole day. Counting in UTC means a day is always exactly 86,400 seconds, which makes the results consistent regardless of where you are.
How many days are in a year on average?
365.2425 in the Gregorian calendar — the average once you account for leap years occurring in years divisible by 4, except centuries, except those divisible by 400. That is the figure used in the decimal years row.
Can I count backwards?
Yes. If the second date is earlier than the first, the headline figure is negative and the breakdown describes the gap. The working days and weeks rows always report the magnitude.