Add / Subtract Durations
Enter durations above to see the result
Add and subtract durations, or measure the exact span between two clock times — all in days, hours, minutes and seconds. Whether you are totaling work shifts, planning travel legs, or figuring out how long it is until a deadline, this calculator normalizes everything into a clean d:h:m:s breakdown with totals in hours, minutes and seconds on the side.
How to Use
- Pick a mode: Choose Add / Subtract or Time Between.
- Add / Subtract: Enter two durations in days, hours, minutes and seconds, then pick the + or − operator. The result updates live.
- Time Between: Enter a start and end time (seconds supported). Optionally add dates on both sides to measure across days.
- Read the result: See the normalized breakdown plus total hours, total minutes, and total seconds.
Features
- Two modes: duration arithmetic and elapsed time between clock times
- Normalized days/hours/minutes/seconds breakdown with negative-result support
- Alternative totals: the same span expressed as total hours, minutes, or seconds
- Overnight times handled automatically — an earlier end time wraps to the next day
- Optional date fields for exact multi-day spans, with strict date validation
- Runs entirely in your browser — no data leaves the page
When to Use Duration Math vs Time Between
Duration arithmetic answers questions like 「two tasks take 1h 45m and 2h 30m — how long in total?」 or 「I have 8 hours and a task took 3h 20m — what is left?」. Time Between answers 「how much time passes from 09:15 to 17:40?」 or 「how many hours between March 1 at 10:00 and March 3 at 14:00?」. The first works with quantities of time; the second works with points in time. Mixing them up is the most common source of off-by-a-day errors, so the two modes are kept deliberately separate.
Use Cases
- Timesheets: Total daily work segments or subtract break time from a shift.
- Travel planning: Add flight, layover, and transfer legs into one trip duration.
- Cooking and sports: Sum stage times or lap splits without mental arithmetic.
- Overnight work: Measure a 22:00 → 06:30 night shift correctly across midnight.
- Countdown checks: See the exact time remaining between now and a future clock time.
Tips for Accurate Results
Use the date fields whenever a span crosses midnight and the specific days matter — without dates, an earlier end time is always treated as the next day. Watch the negative sign: a minus result in Add/Subtract mode means the second duration was larger, and in Time Between mode it means the end datetime is before the start. The total-hours figure is decimal (e.g. 2.5 hours), which is handy for billing or payroll, while the d:h:m:s breakdown is what you would write on a schedule.
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Frequently Asked Questions
What does the Time Calculator do?
It has two modes. The Add/Subtract mode combines two durations written in days, hours, minutes and seconds and shows the result as a normalized d:h:m:s breakdown. The Time Between mode computes the elapsed duration between two clock times, optionally on different calendar dates.
Can the result be negative?
Yes. Subtracting a larger duration from a smaller one, or entering an end date/time before the start in Time Between mode (when both have dates), produces a negative result shown with a minus sign.
What happens if the end time is earlier than the start time?
When no dates are entered, the calculator assumes the end time falls on the next day. For example, 22:00 to 01:30 gives 3 hours 30 minutes. If you want an exact span across specific days, fill in both date fields instead.
Can I enter more than 60 minutes or 24 hours?
Yes. Duration fields are not range-limited — entering 90 minutes simply contributes 5400 seconds, and the result is normalized automatically (90 minutes becomes 1h 30m in the breakdown).
Is my data sent anywhere?
No. All calculations run entirely in your browser. Nothing you enter is uploaded or stored on a server.