What is a time duration calculator?

A time duration calculator calculates the difference between two dates and times, or allows you to add/subtract durations from a given date/time.

How do I calculate the duration between two dates?

Enter the start and end dates/times in the calculator and click the calculate button to get the duration in days, hours, minutes, and seconds.

Can I add or subtract time using this calculator?

Yes, you can add or subtract durations such as days, hours, minutes, and seconds to a specific date/time to get the new date/time.

Who can use the time duration calculator?

It is useful for students, teachers, project managers, event planners, business professionals, and anyone who needs to calculate or manipulate durations.

Time Duration Calculator

Calculate difference between two dates/times, add/subtract durations, and convert durations to hours, minutes, and seconds.

Start Date & Time

End Date & Time

Base Date & Time

Add Duration

Base Date & Time

Subtract Duration

Understanding Time Duration Calculations

Calculate the difference between dates/times or manipulate them by adding/subtracting durations. Learn formulas, examples, and tips for quick mental calculation.

Formulas

Duration: End Date/Time − Start Date/Time
Add Duration: New Date = Base Date + Duration
Subtract Duration: New Date = Base Date − Duration

Example

Start: 2026-01-20 08:00, End: 2026-01-21 10:30 → 1 day, 2 hours, 30 minutes
Add 1d 2h to 2026-01-20 08:00 → 2026-01-21 10:00
Subtract 3h 15m from 2026-01-21 10:30 → 2026-01-21 07:15

Quick Tips

1 day = 24 hours = 1440 minutes = 86400 seconds
1 hour = 60 minutes = 3600 seconds
1 minute = 60 seconds

Quick Reference Table

Duration	Days	Hours	Minutes	Seconds
1 day	1	24	1440	86400
1 hour	0.0417	1	60	3600
30 minutes	0.0208	0.5	30	1800
15 seconds	0.0001736	0.00417	0.25	15