How to use the time duration calculator
- Enter a start time and an end time.
- For spans longer than a day, also enter a start date and end date.
- Read the duration in days, hours and minutes, plus total hours and minutes.
Formula
Same day: duration = end time - start time (add 24 hours if the end is earlier)
With dates: duration = (end date and time) - (start date and time)
Total hours = total minutes / 60
With dates, the calculator uses your device's time zone, so daylight saving changes are counted as real elapsed time.
Worked example: an office day and a clock change
From 9:15 AM to 5:45 PM is 8 hours 30 minutes, which is 510 minutes or 8.50 hours.
Daylight saving example in the Eastern time zone: on March 8, 2026 the clocks jump from 2:00 AM to 3:00 AM. From 1:00 AM to 4:00 AM looks like 3 hours on the wall clock, but only 2 hours really pass. The calculator reports 120 minutes and warns you about the change.
Elapsed time versus clock difference
Subtracting two clock times assumes nothing odd happened in between. On the two nights each year when daylight saving time starts or ends, one hour is skipped or repeated. Elapsed time counts what really passed. If you need the plain clock difference, use times on a day when no change happens.
Common uses
Check how long a flight, a meeting or a shift lasted, count the hours a machine ran or find the gap between two timestamps in a log. If you need only the day count between two dates, use the days between dates calculator, which skips the clock time.
Assumptions and limits
- Without dates, an end time earlier than the start is treated as the next day. Identical times give zero.
- With dates, results depend on the time zone set on your device.
- Date and time values are read in your browser and never sent anywhere.
Frequently asked questions
How many hours between 10 PM and 6 AM?
Eight hours. The end time is earlier than the start, so the calculator assumes the next morning.
Why is my result an hour off across March or November?
Daylight saving time. In the United States clocks move forward in March and back in November, so a span across those nights is one hour shorter or longer than the clock difference.
Can I find the days between two dates?
Yes, but the days between dates calculator is built for that and also shows weeks and months.