Time and Dates
Add or subtract two durations in hours, minutes, and seconds. See a signed result when subtraction passes below zero.
Enter durations, not clock times. Hours may exceed 24; minutes and seconds must each be 00–59.
A duration is an amount of elapsed time, not a time shown on a clock. Adding 23:30:00 and 02:00:00 gives 25:30:00, not 01:30:00, because the hours are not wrapped at midnight. This is useful for workloads, video segments, travel legs, and multi-day activities.
The calculator converts both entries to whole seconds, performs the chosen arithmetic, then converts the total back to hours, minutes, and seconds. That approach makes carry and borrowing explicit: 01:59:50 plus 00:00:20 is 02:00:10, while 01:00:00 minus 00:00:01 is 00:59:59.
A negative answer means the second duration exceeded the first. For example, 00:15:00 minus 00:20:00 is -00:05:00. The sign applies to the entire result, not just the hours field. Enter positive components and use the operation control for subtraction; a typed negative component is deliberately rejected.
This tool does not calculate the difference between two wall-clock appointments. That problem needs dates, time zones, daylight-saving changes, and a rule for crossing midnight. Seconds here are exact arithmetic units, but the accuracy of your source timings remains your responsibility.
| Control | What it does | Important detail |
|---|---|---|
| First duration | Starting amount in HH:MM:SS | Hours may be 0–999999; minutes and seconds 00–59. |
| Second duration | Amount to add or subtract | Always enter a nonnegative duration. |
| Operation | Chooses addition or subtraction | Subtraction computes first minus second. |
| Result | Signed hours, minutes, seconds | Hours do not wrap after 24. |
Total separate work blocks before converting them to a payroll format.
Add clip lengths or subtract a cut from a target runtime.
Combine intervals while retaining seconds rather than rounding to minutes.
It does not apply dates, time zones, breaks, or overtime policy. For clock-in and clock-out work, use a work-hours tool and verify payroll rules.
Yes. A duration can be longer than a day, and the result never wraps to a 24-hour clock.
With subtraction, the second amount is larger than the first; the minus sign belongs to the whole duration.
Each duration is converted to seconds before arithmetic, then decomposed into hours, minutes, and seconds.
No. Use 2:15:00 instead; minutes and seconds are limited to 00–59.
No. It handles durations only, not local times or dates.
Last reviewed: October 23, 2026. Calculations run in your browser. Confirm important results independently.
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