UsefulTab
Time Calculator
Add or subtract times and durations, or find the gap between two times.
Enter a time to calculate
Pick a mode, enter your times, and the result updates instantly in your browser.
Runs entirely in your browserAdd, subtract, and measure time
Switch between three modes. Add/subtract combines a start time with a duration in hours, minutes, and seconds and shows the result. Duration between two times measures the gap, rolling correctly across midnight when you allow it. Everything is computed in your browser with plain arithmetic — the values you type are never uploaded.
Common questions
What can this calculator do?
Three things: add a duration to a start time, subtract a duration from it, and measure the duration between two clock times. Durations are entered as hours, minutes, and seconds.
Does it handle crossing midnight?
Yes. In duration mode, if the end time is earlier than the start time you can treat it as the next day, so an overnight span like 22:00 to 06:00 reads as 8 hours instead of a negative value.
Can I add more than 24 hours?
Yes. In add/subtract mode the duration fields accept any number of hours, so adding 30 hours to a start time rolls the clock forward and reports how many whole days were crossed.
Is my input uploaded anywhere?
No. All calculations run in your browser with JavaScript. The times you enter are never sent to a server or stored anywhere.