CalcCommonsHow to use
For elapsed time, enter start and end clock times, with both dates if the span crosses multiple days. For addition or subtraction, enter the start time and duration components. AM/PM and 24-hour clock inputs are accepted.
For related tasks, try the Work Hours Calculator.
Formula & how it works
Elapsed time = end date/time − start date/time. With no dates, an earlier end time means the next day. Adding or subtracting duration changes the clock time and may produce a day offset.
Worked example
Example 1
23:30 to 01:15 without dates = 1 hour 45 minutes = 1.75 hours = 6,300 seconds.
Assumptions & practical notes
Enter both dates or neither. Clock input accepts HH:MM, HH:MM:SS, and AM/PM.
Dates are treated as uniform 24-hour days. This calculator does not model time zones, daylight-saving changes, or leap seconds.
See our calculation methodology for unit definitions and testing practices.
Frequently asked questions
What does a day offset of −1 mean?
The result is on the previous day relative to your start time.
Do equal times mean 24 hours?
Without dates they mean zero. Supply consecutive dates for a full day.
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