Time duration calculator

Two jobs on one page

Either you have two moments and want to know how far apart they are, or you have one moment and a duration and want to know where you land. Both are here. The first covers timesheets, project spans and how long until something; the second covers deadlines — thirty working days from today, ninety days from an invoice date, forty-eight hours from now.

Elapsed time and calendar time are different

The result shows both, deliberately. Elapsed time is a count of hours and minutes that actually passed — the right answer for billing, for how long a job ran, for anything you are paid by. Calendar time is years, months and days, which is how people describe a span out loud but which does not correspond to a fixed number of hours, because months vary in length and clocks change.

Both are correct answers to different questions, and showing only one is how a calculator ends up disagreeing with a payslip.

Working days, honestly counted

Working days are counted Monday to Friday, with both ends included — which is what leave requests and delivery estimates mean. Public holidays are not subtracted, and that is a deliberate refusal rather than a missing feature. Holidays differ by country, by state, by year and sometimes by industry; a tool that quietly applied one country's calendar to everybody would give a confidently wrong answer to most of its users. Subtract the ones that apply to you.

The count is arithmetic rather than a loop over every day, so a span of fifty years costs the same as a span of five days.

Times as well as dates

Add a time after the date and it is used: 2026-03-14 09:30. Leave it off and midnight is assumed. Leave the start empty and it uses the current moment, which is what you want for "how long until" and "what date is ninety days from now".

Clock changes

Where daylight saving is observed, two local days a year are not twenty-four hours long. Elapsed time here is measured as real elapsed time, so it reflects that; day counts are measured from noon to noon so a clock change cannot push a count over a day boundary. Getting this wrong in either direction is one of the most common quiet bugs in date arithmetic.

Negative durations

Enter the dates in either order. If the end is before the start you get the gap anyway, with a note saying so, rather than a negative number or an error — because that is almost always a typo rather than a question about time running backwards.