Time calculator

Clock math without the head math: add or subtract a duration from any time of day, with results in both 12-hour and 24-hour format.

How to Time calculator

1. Step 1. Enter the starting clock time.
2. Step 2. Choose add or subtract.
3. Step 3. Enter the duration in hours, minutes, and seconds.
4. Step 4. Read the resulting time in both formats.

Frequently asked questions

What happens when I cross midnight?

Times wrap around: 11:00 PM plus 3 hours is 2:00 AM. Subtraction past midnight rolls back into the previous day.

Can I add more than 24 hours?

Yes — durations of any length wrap correctly; 30 hours from 8:00 AM lands at 2:00 PM the next day.

Is the output 12-hour or 24-hour?

Both are displayed side by side for every result.