Time duration calculator

Exact hours and minutes between two date-times, in any time zones, with daylight-saving changes accounted for. Or add a duration to a time.

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Elapsed time vs calendar time

There are two honest answers to "how long between these times?". Elapsed time is what a stopwatch would measure. Calendar time is what the wall clock and calendar say. They differ only when a daylight-saving change or a time-zone difference sits between the two times, and that's exactly when payroll, shift and flight calculations go wrong. The tape shows elapsed hours as the headline and the calendar breakdown underneath, and warns you when they disagree.

Not every day is 24 hours long

Pick a time zone to list the local days that are shorter or longer than 24 hours. Add "1 day" across one of them and you move by the calendar; add "24 hours" and you move by the clock of physics, landing an hour off.

Lord Howe Island shifts by just 30 minutes, giving 23.5 and 24.5-hour days, a reminder never to assume DST means one hour.

Tips for shifts and timesheets

  • Overnight shift: put the end on the next date rather than subtracting clock times.
  • Night shift across the autumn change: the worked time is an hour longer than the rota suggests. The US Fair Labor Standards Act counts hours actually worked.
  • Decimal hours are rounded for display only; minutes and seconds are exact.

Questions people ask

How do I calculate the duration between two times?
Convert both date-times to an exact instant (taking the time zone and daylight saving into account), then subtract. The calculator shows the result as hours and minutes, decimal hours, total minutes and seconds, and as a calendar breakdown.
What about times that cross midnight?
Give each time its own date. 22:00 on the 1st to 06:00 on the 2nd is 8 hours. If both dates are the same, an end time earlier than the start gives a negative duration.
How are daylight saving changes handled?
Each time is read in its time zone using the IANA time zone database in your browser. Across the spring change in New York, noon to noon is 23 hours; across the autumn change it is 25 hours. Times that don't exist (skipped by the spring change) are moved forward, and times that happen twice use the first occurrence.
Can I calculate a flight duration across time zones?
Yes. Enter departure time and zone, then arrival time and zone. For example 09:00 in London to 17:00 in Tokyo on the same date in September is 0 hours, since 17:00 in Tokyo is 09:00 in London.
How do I convert minutes to decimal hours for a timesheet?
Divide the minutes by 60: 7 h 45 min is 7.75 hours. The calculator shows decimal hours for every result.

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