Enter two durations to add or subtract them.
How to Use the Time Calculator
Two durations, each its own hours/minutes/seconds, add or subtract directly, carrying over the same way column arithmetic does past 60.
total seconds = (h × 3600) + (m × 60) + sDurations in hours:minutes:seconds don't add or subtract cleanly by column the way whole numbers do — 45 minutes plus 45 minutes isn't "90 minutes," it's 1 hour 30 minutes, and the carrying has to happen correctly across all three units at once. This Time Calculator converts both durations to total seconds, does the arithmetic there, then converts back — which sidesteps the carrying problem entirely rather than trying to handle it field by field.