Free Time Duration Calculator Online
Add or subtract two time durations. Enter hours, minutes, and seconds to get instant results.
Key Features
Everything you need in one free tool
Switch between addition and subtraction mode with a single click.
Results update automatically as you type. No button press needed.
browser-side workflows is done locally in your browser. Your data stays private.
About This Tool
This tool measures the elapsed time between two clock times or two dates, returning the gap in hours, minutes, and seconds (or in days). It handles spans that cross midnight and, for date mode, spans that cross month and year boundaries where the number of days per month varies.
Manual duration math is error prone because time is base 60 for minutes and seconds and base 24 for hours, not base 10. Subtracting 09:45 from 17:20 in your head is easy to get wrong by an hour. The calculator normalises both inputs to a single unit internally, subtracts, then converts back, so borrowing across the 60 and 24 boundaries is handled for you.
Time zones and daylight-saving changes complicate durations that span them: a period that crosses a clock change can gain or lose an hour, which pure clock arithmetic misses. For spans within a single zone the calculation is exact, so note any zone change separately when it applies.
How to Use It
- Enter the start time or date and the end time or date.
- Choose whether you want the answer in hours and minutes or in whole days.
- The duration appears immediately, including spans that pass through midnight.
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