Duration Calculator
Measure the exact time between two moments — date and clock time for each — and get the duration as days, hours and minutes, plus total hours and minutes for logs and billing. Dates alone? The date calculator handles pure day counts.
How duration is calculated
Both moments are placed on one timeline (days since a reference plus minutes since midnight), subtracted, and the difference is split back into days, hours and minutes. Entering the moments in the wrong order just flips the sign — the calculator swaps them for you.
This page measures elapsed clock time to the minute. It deliberately ignores time zones and daylight-saving shifts — both moments are read on the same clock. For flights across time zones, convert both times to one zone (UTC) first.
Worked examples
Example 1: length of a conference
From November 7, 9:30 AM to November 9, 2:45 PM.
- Two full days from 9:30 to 9:30.Nov 7 09:30 → Nov 9 09:30 = 2 days
- Then from 9:30 to 14:45 on the last day.14:45 − 09:30 = 5 h 15 min
2 days, 5 hours, 15 minutes (53.25 total hours).
Example 2: borrowing across midnight
From 10:00 PM on the 7th to 6:30 AM on the 8th.
- The clock time 06:30 is earlier than 22:00, so borrow a day.1 day − (22:00 − 06:30)
- Compute the remainder.24:00 − 22:00 + 6:30 = 8 h 30 min
8 hours 30 minutes — a classic overnight shift.
Example 3: billing in decimal hours
Work started Nov 7 at 13:15, finished Nov 8 at 10:45 (with sleep ignored by the contract).
- Total elapsed time.21 h 30 min
- Convert to decimal for the invoice.21 + 30 ÷ 60 = 21.5 h
21.5 elapsed hours between the two moments.
FAQ
How is this different from the date and hours calculators?+
The date calculator counts whole days between dates; the hours calculator measures within one day (shifts). This page combines both: date + time to date + time, for durations that span days and carry minutes.
Does it account for time zones or daylight saving?+
No — both moments are read on the same clock, which is what you want for durations in one place. Across zones, convert both to UTC first; during a DST switch night, wall-clock duration can differ from real elapsed time by an hour.
Are both endpoints included?+
Duration is the distance between the two moments — the start instant counts, the end instant is the finish line. There's no ±1 ambiguity like with whole-day counting.
Can I add a duration to a date and time instead?+
Date-plus-days works in the date calculator's add mode. A full "add hours and minutes to a moment" mode is planned here.
Related calculators
- Date CalculatorCount the days between two dates (with weeks and a years/months/days breakdown) or add and subtract days from a date — with the counting logic shown.
- Hours CalculatorCount hours and minutes between two times, subtract unpaid breaks, and convert to decimal hours for payroll. Handles overnight shifts automatically.
- Time Card CalculatorFree weekly time card calculator: enter daily start, end and breaks to total the week's hours in decimal form, with optional gross pay at an hourly rate.