Time Duration Calculator
Pick one of two modes. Two lengths of time adds two times in hours, minutes and seconds, or subtracts the second from the first, and the answer comes back as HH:MM:SS. Clock time plus or minus hours starts from a time of day, so 2 pm minus 5 hours gives 9:00 AM, and it says when the answer falls on another day.
How to use the Time Duration Calculator
- Enter your numbers in the Time Duration Calculator above.
- Press the Calculate button to see the result.
- To try other numbers, change any value and press the button again.
The duration calculation
Seconds = hours × 3,600 + minutes × 60 + seconds · · · Result = Time 1 ± Time 2, written back as HH:MM:SS · · · Clock time: minutes after midnight ± (hours × 60 + minutes), wrapped into 24 hours
The calculator converts both times to seconds, adds or subtracts them, and splits the total back into hours, minutes and seconds. Hours do not wrap at 24, so 20:00:00 + 10:00:00 gives 30:00:00. Each field takes a whole number of 0 or more, and a blank field counts as 0. For half an hour, enter 30 minutes rather than 0.5 hours. Clock time turns the time of day into minutes after midnight, adds or subtracts, and wraps the result into one day, counting each 24 hours it crosses.
Worked example
With the default inputs, 2:30:00 + 1:45:30 = 04:15:30. Switch the operation to minus and 2:30:00 − 1:45:30 = 00:44:30. In Clock time, 2 pm is 840 minutes after midnight, and 5 hours is 300 minutes, so 2 pm minus 5 hours is 540 minutes, or 9:00 AM the same day. 2 pm minus 15 hours is 11:00 PM the day before.
Frequently asked questions
What happens if the second time is longer than the first?
Subtraction then gives a negative duration, shown with a minus sign. 1:00:00 − 2:30:00 returns -01:30:00.
Can I enter more than 59 minutes or seconds?
Yes. The calculator converts every field to seconds before it does the math, so it reads 0:90:00 as 1 hour 30 minutes. 0:90:00 + 0:00:00 returns 01:30:00.
What is 2 pm minus 5 hours?
9:00 AM the same day. Pick Clock time plus or minus hours, enter 2 pm, choose minus and enter 5 hours. The same mode adds hours too, so 10 pm plus 5 hours is 3:00 AM the next day.
Which time formats does Clock time take?
Forms such as 2 pm, 2:30 pm, 2:30 PM, 14:30, noon and midnight. A bare 2 gets a message, because it could mean 2 am or 2 pm. The answer shows both the 12-hour and the 24-hour clock.
Does Clock time handle daylight saving?
No. It counts plain 24-hour days and does not know the date or your time zone, so a clock change in between would move the answer by an hour. For two places at once, use the time zone calculator.
Where can I find the hours between two clock times?
In the hours calculator. It takes a start and an end time of day and returns the hours between them. This page adds or subtracts a length of time and has no calendar.