Time Duration Calculator
Use this free online Time Duration Calculator to find the exact gap between two dates and times in days, hours, minutes and seconds. It is useful for project managers tracking deliverables, employees working out billable hours, students measuring exam preparation time, and anyone planning a countdown to an event. Pick a start moment and an end moment — the calculator handles month-length differences, leap years and your local time zone, then returns both a mixed-unit summary (e.g. '12 days 4 hours 30 minutes') and running totals in each unit. Reverse the dates for a negative duration if you want to count down to a future date. Runs entirely in your browser, no sign-up.
Tips
This tool gives you the exact duration between two moments. Useful for tracking project timelines, age between events, work hours, or countdown remaining to a deadline.
How to Use This Time Duration Calculator
Working out a duration takes four inputs — pick the start and end dates plus the times.
- Pick the start date in the first calendar field.
- Pick the start time, or leave it at midnight to ignore time-of-day.
- Pick the end date and end time using the same controls.
- Click Calculate Duration to see the mixed-unit answer.
- Scroll the breakdown for running totals in days, hours, minutes and seconds — handy for timesheets and contracts.
Example Calculation
From 9:00 am on 1 May 2026 to 5:30 pm on 8 May 2026 is 7 days, 8 hours and 30 minutes — the equivalent of 176 hours, 30 minutes, or 10,590 minutes total. Useful for tracking how many hours you've worked on a project, calculating a contract duration, or counting down to a deadline.
How This Time Duration Calculator Works
Time duration is the gap between two specific moments. The calculator converts both timestamps to milliseconds since the JavaScript epoch (1 January 1970 UTC), subtracts them, and then breaks the difference down into human-readable units. Whole days are computed by integer-dividing the millisecond gap by 86,400,000 (the number of milliseconds in a day). The remainder cascades down into hours, minutes and seconds. Total weeks, total hours and total minutes are also presented so the same span can be expressed in whichever unit your form or contract requires. Negative durations are shown with a leading minus sign so the tool doubles as a countdown. Daylight-saving transitions can shift wall-clock time by an hour twice a year, which means a span that crosses a DST boundary may report a wall-clock duration that differs from the true elapsed time by 60 minutes. For DST-aware conversions across multiple zones use the Time Zone Converter; for raw elapsed time this calculator is precise to the millisecond.
Last updated: May 2026.
Frequently Asked Questions
How many seconds are in a day?
86,400 seconds (60 × 60 × 24). The calculator includes total-seconds in its results so you can verify or use this directly.
Does this account for daylight saving time?
It uses your local time zone but treats both timestamps as wall-clock values. If your span crosses a DST boundary, the wall-clock duration may differ slightly from the actual elapsed time. For DST-aware conversions use the Time Zone Converter.
Can the result be negative?
Yes — if the end date is earlier than the start, the duration is shown with a minus sign so you can use it for countdowns.
What's the difference between a date and a duration?
A date is a fixed point in time; a duration is the gap between two dates. "Today is May 6" is a date; "3 weeks from now" is a duration applied to today.
Can I calculate working hours with this?
You can calculate the raw span between clock-in and clock-out times. To exclude weekends or breaks, do that subtraction manually after reading the result.