Time Calculator

It works in three modes: add a duration to a start time, subtract a duration from a start time, or find the elapsed time between two clock times. All results are shown in hours, minutes, and seconds (HH:MM:SS).

The calculator tracks 24-hour day boundaries automatically. If adding time pushes the clock past midnight (00:00), it wraps the clock and reports how many full days you crossed forward. Subtracting past 00:00 wraps backward and shows a negative day count. It has no date or timezone input, so it does not model daylight saving time.

Yes. If the end time you enter is earlier than the start time (for example, start 22:00 and end 06:00), the calculator treats the end as the following day and returns the correct elapsed duration of 8 hours.

Enter times in 24-hour format as HH:MM (for example, 14:30 for 2:30 PM). Both single-digit hours like 9:00 and two-digit hours like 09:00 are accepted. Results always display as HH:MM:SS.

Yes. In add and subtract modes you can enter hours, minutes, and seconds independently, so you can shift a time by any combination, such as 1 hour, 45 minutes, and 30 seconds at once. Duration mode accepts only HH:MM for the start and end times.