How to use the time duration calculator
- Enter the start date and start time.
- Enter the end date and end time. A blank time counts as midnight at the start of that day.
- Read the duration in days, hours and minutes, and the same length of time as total days, hours, minutes and seconds. For periods of a month or more, the calculator also shows it in calendar months.
If the end is earlier than the start, the calculator swaps them and tells you, so you still get the length of the gap.
How the duration is calculated
Both moments are turned into a count of seconds on a single timeline, so month lengths and leap years are handled exactly: February 28 to March 1 is 2 days in 2024 and 1 day in 2026. The calendar breakdown counts whole months forward from the start, like an age, then shows the days, hours and minutes left over.
Worked example
The calculator opens with a start of 8:00 AM today and an end of 5:30 PM two days later. Taking October 29 to October 31, 2026:
- 8:00 AM on October 29 to 8:00 AM on October 31 is 2 days.
- 8:00 AM to 5:30 PM is another 9 hours 30 minutes.
- The duration is 2 days 9 h 30 min.
- Total hours: 2 × 24 + 9.5 = 57.5 hours.
- Total minutes: 57.5 × 60 = 3,450. Total seconds: 3,450 × 60 = 207,000.
- Total days: 57.5 ÷ 24 = 2.3958 days.
A night shift from 10:00 PM on March 7 to 6:15 AM on March 8, 2026 is 2 hours to midnight plus 6 h 15 min, so 8 h 15 min on the clock.
Clock time vs. elapsed time
This calculator measures clock time: the difference between what two clocks show, with every day counted as 24 hours. That is what you want for nearly every question, from how long until a flight to how many hours a project took.
Elapsed time differs only when the period crosses a daylight saving change in your location. In New York, clocks jumped from 2:00 AM to 3:00 AM on March 8, 2026, so the night shift in the example above really lasted 7 h 15 min, not 8 h 15 min. Payroll rules usually pay for the hours actually worked, so check how your employer handles the change. The two nights a year when it matters are listed in the time zone calculator.
| From | To | Duration |
|---|---|---|
| Jan 1, 2026, 9:00 AM | Jan 1, 2027, 9:00 AM | 365 days (8,760 hours) |
| Feb 28, 2024, 12:00 AM | Mar 1, 2024, 12:00 AM | 2 days (leap year) |
| Oct 29, 2026, 8:00 AM | Dec 25, 2026, 6:00 PM | 57 days 10 h (1,378 hours) |
Frequently asked questions
How do I calculate the time between two dates and times?
Find the whole days between the dates first, then add or subtract the difference between the clock times. From 8:00 AM Thursday to 5:30 PM Saturday is 2 days, plus 9 hours 30 minutes. If the end time is earlier in the day than the start time, take one day off and add 24 hours to the end time before subtracting.
How many hours are between two dates?
Multiply the whole days by 24 and add the extra hours. 2 days 9 h 30 min is 2 × 24 + 9.5 = 57.5 hours. The calculator shows this as the total hours under the main answer.
Can I count only working hours?
Not with this tool, which counts every hour on the clock, including nights and weekends. For a work shift, use the hours calculator; for a full week of shifts, use the time card calculator.
Why does the calendar breakdown sometimes show fewer days than I expect?
Months have different lengths, so the calendar view counts whole months from the start date first. January 31 to March 1, 2026 is 1 month and 1 day (via February 28), even though it's 29 days in total. The total days figure is always the exact count; for date-only questions, the date calculator gives the same breakdown.
Related calculators
- Time Calculator — Add or subtract days, hours, minutes and seconds from a time, combine two durations, or convert between time units.
- Date Calculator — Add or subtract years, months, weeks and days from a date, or count the days and weekdays between two dates.
- Hours Calculator — Hours worked between a start and end time, minus an unpaid break, in hours and minutes and in decimal hours.
- Day Counter — Count the days or weekdays between two dates, with or without the end date, or count down the days to an event.
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