Online Time Duration Calculator
Working out how long sits between two moments by hand is easy to get wrong - especially across midnight, across dates, or across time zones. This time duration calculator returns the exact gap between a start and end point in hours, minutes, and seconds, then breaks the same span into total minutes, seconds, days, weeks, and percent of a year. It's free and needs no signup.
How to use the Time Duration Calculator?
Select your start and end date to calculate the time duration between them.
Use the Time fields
If you don't want full dates, you can use the time fields by giving hours, minutes, and seconds to calculate time duration between two times.
- Dates supported: January 1, 0001 to December 31, 9999.
- The Julian calendar is used before September 3, 1752; the Gregorian calendar after.
- The 11-day correction in September 1752 (September 3-13) is accounted for automatically.
- Daylight Saving Time is not considered (default mode).
Time zone option
To compare time across countries, choose the times along with their respective locations on which you want to compute the time duration.
- Dates supported: January 1, 0001 to December 31, 9999.
- Dates before 1582 are interpreted using Gregorian rules (Julian not supported in this mode).
- Daylight Saving Time (DST) is supported.
Pick a Time format
Select 12-hour (AM/PM) or 24-hour and enter the time accordingly.
Time Standards
UTC (Coordinated Universal Time)
UTC is the global reference standard used to define time zones. Many systems convert local times to UTC internally, then compute the result.
GMT (Greenwich Mean Time)
GMT is a historical reference time standard tied to the Prime Meridian (0° longitude). In practical use, GMT is often treated as the same reference as UTC for everyday timekeeping.
This tool performs time zone calculations based on UTC offsets.
What you can use it for
A time duration calculator removes the manual errors that creep in when you count by hand. Common uses:
- Measure the exact gap between two events, deadlines, or project milestones - down to the second.
- Compare planned versus actual time spent on a task or shift.
- Plan and compare schedules across countries with the time-zone mode.
- Convert a single span into total seconds, minutes, hours, days, or weeks for logs and reporting.
- Work with historical dates accurately, including the Julian-to-Gregorian calendar transition.