How this calculator works
Clock times repeat every day, so two bare times cannot say how long the gap is: 22:00 to 06:30 could be 8.5 hours or 32.5 hours. Here each reading carries its own date and UTC offset, which pins down the exact instants before they are subtracted. That also makes the answer correct when the clocks change between the two readings.
Formula
Each reading becomes U(x) = 86400 x (O(date) - 1) + 3600h + 60m + s - offset_seconds. The hours between are (U(end) - U(start)) / 3600, with the duration string built from the whole-second remainder.
Worked example
22:00 on 2026-10-31 with offset -04:00 to 06:30 on 2026-11-01 with offset -04:00 is 30600 seconds, or 8.500000 hours. The same clock pair in a daylight-saving change would differ by one hour because the offsets would not match.
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Frequently asked questions
Why do I need dates if I only care about the clock?
The date is what distinguishes an overnight gap from a multi-day one. With dates, an earlier end time is never silently treated as the next morning.
Can I get minutes instead of hours?
The duration line already shows hours, minutes and seconds, and the seconds figure can be divided by 60 for minutes.
What if the end is before the start?
The page reports an error, because a negative elapsed time is usually a sign that the dates or offsets were entered the wrong way round.