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 shows the same span as total hours, total minutes, and total seconds - with year, month, and day breakdowns for longer spans. 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 up to October 4, 1582 and the Gregorian calendar from October 15, 1582 - the original calendar reform.
- The 10-day correction of October 1582 (October 5-14) is applied automatically, and each result is labelled with the calendar it used.
- 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.
- Each city applies the Julian-to-Gregorian adoption date for its country instead of the 1582 default; 56 countries are covered.
- Offsets from 1970 onward come from the time zone database, including daylight saving; earlier dates use a historical offset table or local mean time, so treat pre-1970 results as close rather than exact.
- 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GMT is a historical reference time standard tied to the Prime Meridian (0° longitude).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, or hours for logs and reporting.
- Work with historical dates accurately, including the Julian-to-Gregorian calendar transition.