A time duration calculator measures the clock distance between a start time and an end time. The easy case is 09:00 to 17:00: eight hours. The useful case is 22:15 to 06:45 the next morning. A tool that assumes the end must be later on the same calendar day will either error or print a negative duration. This page adds 24 hours when the end is the same as or earlier than the start, and the status says the span crossed midnight.
Results are hours, minutes, seconds, and a short phrase. There is no timezone picker, no DST database, and no “meeting across New York and Dubai” mode. Those are converters. This is a duration tool. Multi-day spans belong on the Date Difference Calculator, which works with calendar dates rather than clock times.
Equal start and end is treated as a full overnight wrap (24 hours). The two-field UI cannot tell “zero minutes on the same shift” from “a shift that lands on the same clock tomorrow.” The status makes the wrap visible so you can decide if that is the interval you meant.
Browser time controls vary. The parser accepts HH:MM and HH:MM:SS. Values such as 24:00 or 7:60 are rejected.
Convert each time to seconds after midnight. If end > start, duration = end − start. Otherwise duration = end + 86400 − start. Split the total back into hours, minutes, and seconds. No date is attached. A 26-hour shift needs a date pair plus a time pair; this page will not invent the extra day.
09:00:00 to 17:30:00 → 8h 30m 0s, same calendar day. 22:15:00 to 06:45:30 → 8h 30m 30s, overnight. 14:00 to 14:00 → 24h 0m 0s, wrap. Empty fields and illegal times stay in the status line.
22:15:00 → 06:45:30
= 8 hours, 30 minutes, 30 seconds (overnight)A night shift that starts at 22:00 and ends at 06:00 is eight hours whether or not you think of it as “yesterday” or “today.” Attach dates only when the shift can exceed 24 hours or when you need the calendar day of the end. Combining this page with the date-difference page by hand (one night plus leftover clock time) is honest. Inventing a timezone offset to fake that combination is not what these fields are for.
Seconds matter for media length and for some payroll clocks. If your inputs are HH:MM only, seconds are zero and the seconds row will show 0. That is not “approximately zero”; it is exact for the times you typed. If a timesheet stores tenths of an hour, convert after you have hours and minutes; this page will not emit 7.5 hours unless you divide 7h 30m yourself.
To count calendar days, including exclusive versus inclusive, use the Date Difference Calculator. That page will not read 22:15. This time duration calculator will not read 2024-01-31.
If the end time is the same as or earlier than the start, the duration crosses midnight (up to 24 hours). This is not a timezone converter.
The duration is assumed to cross midnight. 22:00 to 06:00 is 8 hours, not a negative span.
That is treated as a 24-hour wrap, not zero. A true zero-length interval would be the same clock on the same shift with no overnight, which this simple two-field tool cannot see.
No. It is a duration between two times of day, not a zone converter.
No. HH:MM is accepted and seconds default to 0.
