Time duration calculator

Enter two times and get the gap between them three ways: as a decimal, as hours and minutes, and as total minutes. A second time earlier than the first is read as the next day.

Crossing midnight is the case worth being careful about. Subtracting clock times directly gives a negative number when the end is on the next day, which is why so many spreadsheets show a stream of hashes for a night shift. Adding twenty-four hours to a negative result is the fix, and it is what happens here automatically. The remaining ambiguity is genuinely unresolvable: 09:00 to 09:00 could be zero or twenty-four hours. This reads it as twenty-four, on the grounds that nobody asks how long it is between a time and itself.