Time Duration Calculator
Find the exact time between two dates and times — broken down into days, hours, minutes, and seconds, with totals in every unit. Free, instant, no signup.
Pick a start and end date and time to see the duration between them.
Stop doing this math by hand
Chronoid tracks every app, website, and document you work in — automatically. See exactly where your hours go, then turn them into invoices in one click. 100% local and private, one-time purchase.
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How to calculate time duration
To find the duration between two moments, subtract the start from the end. Say a project kicked off on Monday at 9:15 AM and wrapped up on Wednesday at 2:45 PM. From Monday 9:15 AM to Wednesday 9:15 AM is exactly 2 days; from 9:15 AM to 2:45 PM adds another 5 hours 30 minutes. Total: 2 days, 5 hours, 30 minutes — or 53.5 total hours.
Doing that by hand gets error-prone the moment a span crosses midnight, a month boundary, or a daylight saving change. This calculator works from the exact timestamps, so you just pick the two moments and read off the answer — including the decimal totals payroll and billing systems want.
Common uses
Shift lengths: enter clock-in and clock-out to get hours worked, including overnight shifts that cross midnight. Project phases: measure how long a sprint, milestone, or engagement actually ran from kickoff to delivery. Event countdowns: set the end to a launch, deadline, or wedding date and see exactly how much time is left. SLA windows: check whether a ticket was resolved within its response window by comparing the opened and closed timestamps.
Frequently Asked Questions
- How is the duration between two dates calculated?
- The calculator subtracts the start moment from the end moment to get the exact elapsed time in milliseconds, then converts it into a breakdown of days, hours, minutes, and seconds, plus running totals in each unit. Because it works from the precise timestamps rather than counting calendar days, the result is exact — a duration from 11:30 PM to 12:15 AM correctly shows 45 minutes, not "1 day".
- Does the calculator handle daylight saving time?
- Yes. It uses your local timezone's actual clock times via the browser, so a span that crosses a daylight saving change reflects the real elapsed time. For example, the night the clocks "spring forward" in the US, 1:00 AM to 4:00 AM is only 2 real hours — and that's what the calculator shows.
- How do I calculate a duration across midnight?
- Just set the correct dates on each field. Because the inputs include both the date and the time, an overnight span like 10:00 PM on March 3 to 6:30 AM on March 4 is calculated automatically as 8 hours 30 minutes — there is no special handling needed for crossing midnight.
- How do I convert a duration to decimal hours?
- Use the "Total hours" figure in the results grid — it is already the decimal form. To do it by hand, divide the minutes by 60 and add them to the hours: 7 hours 45 minutes is 7 + 45/60 = 7.75 hours. Decimal hours are what most payroll and invoicing systems expect.
- How do I know how long I actually spent on a project?
- A duration calculator only helps if you remember when you started and stopped — and most people don't. Chronoid is a Mac app that measures real time in every app, website, and document automatically, so you get exact per-project durations without writing anything down. It's 100% local and private, with a 7-day free trial and a $49 one-time purchase.