EpochLab

Duration Calculator

How long is that, exactly?

A duration in every unit from nanoseconds to decades, with the approximate ones flagged as approximate — because a month has no fixed length and any tool that pretends otherwise is guessing.

Questions people ask

The things that come up about duration calculators, answered plainly.

Why are months and years marked approximate?

Because they have no fixed length. A month is 28 to 31 days; a year is 365 or 366. The totals use the mean Gregorian month (30.436875 days) and year (365.2425 days), which is the best any single number can do — the calendar breakdown above is the exact answer.

What is a fortnight in this list?

Exactly 14 days. It is included because it is one of the few compound units that is genuinely fixed, unlike a month.

Related tools

How far apart two instants are — in whichever unit you need, counting every day or only the working ones.

Date Duration CalculatorThe duration of a range stated the way a person would state it, plus the exact totals underneath and a census of which weekdays fall inside it.
Elapsed Time CalculatorPick a moment and watch the time since it climb, second by second. The page keeps ticking, so it works as a running clock on anything you have started.
Date Interval CalculatorThe interval in every unit at once, plus its midpoint, its ISO 8601 duration string and the calendar breakdown — one page for measuring a span and quoting it.
Date Difference CalculatorEnter two dates and get the gap in every unit at once — years, months and days as a person would say it, and the exact total in weeks, hours, minutes and seconds underneath.

All 160 tools · More in date difference & duration