Time Duration Calculator
- Updated
- Formula shown
- Free, no sign-up
Results
73 d 8 h 30 min from Jan 1, 2026 9:00 AM to Mar 15, 2026 5:30 PM
Both times are read as clock times in the same time zone. If a daylight-saving change falls in between, the real elapsed time is an hour more or less.
How to use the time duration calculator
- Enter the start date and time. Leave the time at 00:00 to start at midnight.
- Enter the end date and time. If the end is earlier than the start, the result is shown as negative.
- Read the duration in days, hours and minutes, then the calendar breakdown and the totals in each unit underneath.
Duration formula
Days = ⌊T ÷ 86,400⌋ · hours = ⌊(T mod 86,400) ÷ 3,600⌋ · minutes = ⌊(T mod 3,600) ÷ 60⌋
Total hours = T ÷ 3,600 · total weeks = T ÷ 604,800
Each date becomes a day number (a count of days from a fixed starting date in the Gregorian calendar) and each time becomes seconds after midnight. Subtracting gives the exact gap in seconds, T, which is then split into days, hours and minutes or divided into any unit. The calendar breakdown counts whole months from the start first, keeping the time of day, and then the days, hours and minutes left over, so it reads the way people describe periods ("2 months and 2 weeks").
Worked example
From Thursday, January 1, 2026 at 9:00 AM to Sunday, March 15, 2026 at 5:30 PM. The day numbers are 73 days apart (31 days in January, 28 in February and 14 in March), and 5:30 PM is 8 hours 30 minutes after 9:00 AM. So T = 73 × 86,400 + 30,600 = 6,337,800 seconds.
That is 73 days, 8 hours and 30 minutes, or 1,760.5 hours, 105,630 minutes and 10.479 weeks. In calendar units it is 2 months, 14 days, 8 hours and 30 minutes: March 1 at 9:00 AM is exactly two months after the start.
Hours in each month of 2026
| Month | Days | Hours | Minutes |
|---|---|---|---|
| January | 31 | 744 | 44,640 |
| February | 28 | 672 | 40,320 |
| March | 31 | 744 | 44,640 |
| April | 30 | 720 | 43,200 |
| May | 31 | 744 | 44,640 |
| June | 30 | 720 | 43,200 |
| July | 31 | 744 | 44,640 |
| August | 31 | 744 | 44,640 |
| September | 30 | 720 | 43,200 |
| October | 31 | 744 | 44,640 |
| November | 30 | 720 | 43,200 |
| December | 31 | 744 | 44,640 |
The whole of 2026 is 8,760 hours; a leap year such as 2028 is 8,784.
Clock time and daylight saving
This calculator measures clock time: both readings are taken as being in the same time zone, with no clock change in between. That is usually what you want for opening hours, rentals and countdowns. Across a daylight-saving change, though, the real elapsed time differs by an hour:
| Place | Period | Clock hours | Real hours |
|---|---|---|---|
| New York | Noon Mar 7, 2026 to noon Mar 8, 2026 | 24 | 23 |
| New York | Noon Oct 31, 2026 to noon Nov 1, 2026 | 24 | 25 |
| London | Noon Mar 28, 2026 to noon Mar 29, 2026 | 24 | 23 |
| London | Noon Oct 24, 2026 to noon Oct 25, 2026 | 24 | 25 |
If the start and end are in different time zones, such as a flight, first convert both to one zone with the time zone calculator, then measure the duration.
Tips
- Midnight belongs to the next day. "Until the end of Friday" means Saturday at 00:00, not Friday at 00:00.
- Use total hours for billing. Rates per hour or per day are easier to apply to a single decimal figure than to a months-and-days breakdown.
- Counting whole days only? The day counter can include the end date or skip weekends, and the date calculator adds days to a date.
Frequently asked questions
How do I calculate the time between two dates and times?
Convert both to the same unit, such as minutes since a fixed starting point, and subtract. From January 1, 2026 at 9:00 AM to March 15, 2026 at 5:30 PM is 73 days, 8 hours and 30 minutes, which is 1,760.5 hours or 105,630 minutes.
How many hours are in a month?
It depends on the month: 672 hours in a 28-day February, 696 in a leap-year February, 720 in a 30-day month and 744 in a 31-day month. A common year has 8,760 hours and a leap year 8,784.
What does "2 months, 14 days" mean when months have different lengths?
The calculator counts whole calendar months from the start first, then the days and hours left. January 1 at 9:00 AM plus 2 months is March 1 at 9:00 AM, and from there to March 15 at 5:30 PM is 14 days, 8 hours and 30 minutes. The total in days avoids the question of month length altogether.
Does the duration allow for daylight saving time?
No. Both times are treated as clock times in one time zone, which is what most people mean. If the clocks change in between, the real elapsed time differs by an hour: in New York, noon on March 7 to noon on March 8, 2026 is 24 hours on the clock but 23 hours in reality.
Can I measure durations across several years?
Yes, between any dates from year 1 to 9999. February 29, 2024 to February 29, 2028 is exactly 4 years, or 1,461 days (35,064 hours), which is 4 × 365 days plus one leap day.