ToolwebHow to use this tool
- Choose duration arithmetic or elapsed time between clock readings.
- Use H:MM:SS for durations and a 24-hour format for clock readings.
- Decide whether an earlier ending time means the next day, then compare the result units.
A task ending after midnight
- Input and settings
- Clock times; 22:30 to 01:15; next-day option enabled
- Result
- 02:45:00; 165 minutes; 9,900 seconds
Without the next-day option, the same-day difference is negative 21 hours 15 minutes.
Distinguish durations from clock readings
In duration mode, 01:30 means one hour and thirty minutes, not one minute and thirty seconds. Include all three groups, as in 00:01:30, to specify seconds. Milliseconds are accepted and totals can exceed 24 hours without wrapping.
Clock mode compares wall-clock readings from 00:00 to 23:59 without dates. If the ending time is earlier, the next-day choice adds 24 hours. Two identical clock readings still give zero, rather than an assumed full day.
Read the same duration in different units
The headline uses H:MM:SS, while the rows show total seconds, total minutes, decimal hours and 24-hour days. The 15-minute component in 02:15:30 is not the total duration in minutes, so use the appropriate total row when filling another form.
A negative duration represents subtraction or a reverse difference. This model does not handle time-zone conversion, daylight-saving transitions, dated timestamps or leap seconds. It answers a different question from the calendar-date calculator.
Common questions
Can I enter 90:00?
In duration mode it means 90 hours. A clock input is instead limited to readings within one day, from 00:00 to 23:59.
Do identical start and end times imply the next day?
No. Identical readings give zero. The next-day adjustment applies only when the ending clock reading is earlier.