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Time Calculator: Add, Subtract, & Diff Time Durations.

Method: Convert intervals into seconds, perform addition/subtraction, then divide back: 3600 seconds per hour, 60 seconds per minute.

Calculator
Calculate Duration or Add/Subtract Time
Result

Working with time arithmetic can be tricky because time uses a sexagesimal (base-60) system for minutes and seconds, and a 24-hour cycle for days.

The Time Calculator simplifies this by allowing you to add or subtract time intervals, or calculate the exact duration between a start and end time.

Whether you are logging work hours, calculating flight durations, or summing up video clips, this tool converts components into a base second metric and outputs clean durations.

Designed for simplicity and speed, the outputs are formatted clearly into total hours, minutes, and days so you can record findings without conversion mistakes.

Worked examples

See the method in action

Example inputs and outputs using the calculator logic.

Input
Add: 3h 45m and 1h 30m
Output
5 hours, 15 minutes
Input
Difference: Start 09:15 AM, End 04:30 PM
Output
7 hours, 15 minutes
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FAQs

Common questions

Answers to help you use the calculator correctly.

How does the AM/PM difference work?

The system converts standard 12-hour clock times into a 24-hour format (e.g. 4:30 PM is 16:30) and calculates the elapsed time within the day.

Can this calculate differences across multiple days?

Yes, if the end time is on the next day, it calculates the elapsed time by adding 24 hours to the boundary calculations.