How Time Duration Calculator works

Calculate time between clock times or date-times, handle overnight spans explicitly, and add a duration to a time.

The formula

Clock times are converted to seconds from midnight; date-times are compared as entered local calendar values.

A practical example

09:30 to 17:45 is 8 hours 15 minutes. Marking 23:00 to 02:00 as next day gives 3 hours.

Important limitations

This tool calculates elapsed entered time without timezone conversion. Use Time Zone Converter when locations or DST matter.

Frequently asked questions

Does an earlier end time automatically mean tomorrow?

No. Select End is next day so overnight intent is explicit.

Is this the Time Unit Converter?

No. This calculates elapsed spans; the converter changes a duration value between seconds, minutes, hours and other units.