Finding how much time passed between two clock times is straightforward when both fall on the same day — but it needs an extra step the moment the interval crosses midnight.
Same-day example
From 9:30 to 17:45, the duration is 8 hours 15 minutes (495 minutes total) — the hours and minutes are simply subtracted, borrowing an hour if the end minutes are smaller than the start minutes.
Crossing midnight
From 22:00 to 06:00 the following morning, the duration is 8 hours 0 minutes (480 minutes) — even though the end time (06:00) is numerically smaller than the start time (22:00). A correct calculation recognizes that the end time belongs to the next day and adds 24 hours before subtracting, rather than returning a negative or nonsensical result.
Common mistakes
- Subtracting the times directly when the end time is smaller, which gives a negative duration instead of correctly wrapping to the next day — this is the single most common error for overnight shifts.
- Mixing up hours and minutes when converting the result to a single unit (like total minutes) — always convert both components before combining.
Enter any start and end time, including overnight intervals, with the Time Duration Calculator.