How to use this calculator
Compare clock times, compare UTC timestamps, add or subtract duration expressions, or shift a UTC timestamp. Clock inputs accept AM/PM and optional seconds. Duration expressions are parsed as units, never evaluated as code. Multiple intervals are added as entered, including overlaps. Each row can deduct its own break. The separate break setting is deducted once from the combined total.
- Enter time task, start time, end time and review the remaining options.
- Select Calculate or change a value to update the result. Read the result label and units before copying.
- Use Reset to restore the worked starting values.
Formula and method
Clock mode uses wall-clock time. UTC date/time modes are elapsed UTC arithmetic; no local timezone or daylight-saving ambiguity is inferred.
Worked example
09:00 to 17:30 is 8 hours 30 minutes.
Questions about time duration calculator
How do I calculate a duration across midnight?
Enter the later evening start and earlier morning end. The automatic option treats the end as next day: 22:00 to 06:00 is 8 hours. Select Always next day when that is the intended interval. Daylight saving shifts are not included.
What assumptions should I check?
Clock mode uses wall-clock time. UTC date/time modes are elapsed UTC arithmetic; no local timezone or daylight-saving ambiguity is inferred.
Are my inputs saved?
Calculations run in your browser. We store only tool IDs for favorites and recent tools. A calculation link contains your inputs only when you explicitly choose to copy one.