Time Duration Calculator
Find the time between two clock times (including overnight spans) or between two dates and times, shown as hours, minutes and seconds and as decimal hours, minutes and days, with a clearly stated rule for midnight and daylight-saving changes.
Change the values and press Calculate to work out your own figures.
Between two times
Find how long it is from one clock time to another. If the end time is earlier, it is taken to be the next day, so overnight shifts work too.
Show the working
- In 24-hour time: 08:30 to 17:30.
- Difference: 32400 seconds = 9 hours.
Between two dates and times
Find the time between two dates, with optional times. Every day counts as 24 hours unless you pick a time zone, which accounts for daylight-saving changes.
How to work out the time between two times
- Type the start and end times, for example 8:30 AM and 5:15 PM. Switch the time format to 24-hour if you prefer 08:30 and 17:15. Seconds are optional (8:30:15 PM).
- If the end time is earlier than the start, the calculator assumes it is on the next day, so a night shift from 10 PM to 6 AM is 8 hours.
- For spans longer than a day, use the second calculator and enter the dates as well.
The answer is shown in hours, minutes and seconds, and as decimal hours and minutes, which is what most timesheets and payroll systems need. For example, 8:30 AM to 5:15 PM is 8 hours 45 minutes, or 8.75 hours.
Converting to decimal hours
Decimal hours = hours + minutes ÷ 60 + seconds ÷ 3600 45 minutes = 45 ÷ 60 = 0.75 hours 7 hours 20 minutes = 7 + 20 ÷ 60 = 7.333333 hours
Midnight and equal times
12:00 AM is midnight at the start of the day and 12:00 PM is noon. When the start and end times are the same, the calculator gives 0 by default; choose "A full day has passed" if you mean the same time the next day (24 hours). A time of 24:00 isn't accepted: use 00:00 with the next day's date instead.
Daylight-saving time
By default every day counts as 24 hours, which gives the difference between the two clock readings. When the clocks change in between, the real time that passed is an hour more or less. Choose a time zone to get the real elapsed time: in New York, from 11 PM on 7 March 2026 to 3:30 AM on 9 March is 28.5 hours on the clock but 27.5 hours in real time, because the clocks went forward on 8 March.
With a time zone chosen, a time skipped when the clocks go forward (such as 2:30 AM on the spring change in the US) is rejected, and for a time that happens twice when they go back you can choose the first or second occurrence. Time-zone rules come from your browser, which keeps them up to date.
Questions
How many hours is 9 AM to 5 PM?
8 hours. From 9 AM to 12 PM is 3 hours and from 12 PM to 5 PM is 5 more.
How do I calculate hours worked overnight?
Enter the start and end times as they appear on the clock. When the end time is earlier than the start, the calculator counts it as the next morning, so 10 PM to 6 AM gives 8 hours.
Are leap seconds included?
No. Like almost all clocks and computer systems, the calculator treats every minute as exactly 60 seconds.
Sources
Limitations
- Wall-clock mode (the default) treats every day as 24 hours: across a DST change the result is the clock difference, which differs from real elapsed time by the DST shift (usually 1 hour). Choose a time zone for real elapsed time.
- Leap seconds are ignored in both modes.
- Times-only mode cannot span more than 24 hours; use the dates-and-times mode for longer spans.
- Historical time-zone offsets are only as accurate as the bundled IANA tzdb release; dates before about 1970 may be less reliable.
- '24:00' as an end-of-day time is not accepted; use 00:00 on the following date.