Time & Date
Time Duration Calculator
Add or subtract hours, minutes, and seconds, or find the exact duration between two times of day.
Duration
8h 30m
How the Time Duration Calculator works
Choose whether you want the duration between two times, or a new time after adding or subtracting hours and minutes. The result updates instantly as you type.
Frequently asked questions
Can this handle times that cross midnight?
Yes — if the end time is earlier than the start time, it's treated as crossing into the next day.
Can I add or subtract time from a starting point?
Yes — switch to "Add / subtract time" mode to add or remove hours and minutes from a starting time.
Guides that cover this
Mastering Dates, Deadlines, and Time ZonesThe everyday date math — ages, countdowns, business days, time zones — that's easy to get wrong by hand.Adding and Subtracting Time Across Hours and Minutes CorrectlyA worked example showing how to correctly add and subtract times that cross an hour boundary, using base-60 borrowing.Why Adding Times by Hand Keeps Giving the Wrong TotalThe specific base-60 borrowing mistake responsible for most manual time-addition errors, and how to catch it.12-Hour vs. 24-Hour Time: Avoiding AM/PM Mistakes in Duration MathWhy calculating a duration is more error-prone in 12-hour AM/PM format than in 24-hour format, and how to avoid the common mistakes.How to Use the Time Duration CalculatorA quick walkthrough of adding, subtracting, or finding the duration between two times.Time Duration Calculator: How It Works and How to Use ItA quick guide to the time duration calculator — what it calculates, how the math works, and tips for getting an accurate result.