What the calculator measures
Two date-times define two instants; their difference is a duration, which the calculator states in whichever unit is useful — a shift in hours and minutes, a project in days and hours, a life in years, months and days. Both moments are taken in your device's local time. The total is exact to the minute; the calendar line (years, months, days plus the remaining hours and minutes) follows the same conventions as the age calculator.
| From → to | Duration | Hours | Minutes |
|---|---|---|---|
| Mar 10, 2026 9:00 AM → Mar 10, 2026 5:45 PM | 8 h 45 min | 8.75 | 525 |
| Mar 10, 2026 10:00 PM → Mar 11, 2026 6:30 AM | 8 h 30 min | 8.5 | 510 |
| Mar 6, 2026 2:00 PM → Mar 9, 2026 9:00 AM | 2 d 19 h | 67 | 4,020 |
| Jan 1, 2026 0:00 → Jul 1, 2026 0:00 | 181 d | 4,344 | 260,640 |
| Sep 10, 2026 12:00 PM → Dec 25, 2026 8:00 AM | 105 d 20 h | 2,540 | 152,400 |
Daylight saving time
Because the calculation uses real instants rather than clock arithmetic, a day on which clocks change is 23 or 25 hours long, and the result reflects it. Noon on the Saturday before the US spring change to noon Sunday is 23 hours. Over long spans the two changes each year cancel out.
| Range | Actual duration | Naive clock arithmetic |
|---|---|---|
| Mar 7, 2026 12:00 → Mar 8, 2026 12:00 (US spring forward) | 23 h | 24 h |
| Oct 31, 2026 12:00 → Nov 1, 2026 12:00 (US fall back) | 25 h | 24 h |
| Any other consecutive noon to noon | 24 h | 24 h |
Time zones
Both times are read in the same zone — yours. For a duration between events in different zones, convert both to one zone (UTC is the usual choice) first. Flight times are the classic case: a New York to London overnight flight shows a clock difference of over twelve hours but lasts about seven.
| Event | Local clock | UTC |
|---|---|---|
| Depart New York (EST, UTC−5) | Mar 10, 6:00 PM | Mar 10, 11:00 PM UTC |
| Arrive London (GMT, UTC+0) | Mar 11, 6:15 AM | Mar 11, 6:15 AM UTC |
| Clock difference | 12 h 15 min | |
| Actual duration (UTC) | 7 h 15 min |
Seconds, minutes, hours, days
The result lists the duration in every unit down to seconds. The fixed conversions are below; a month is not a fixed unit, which is why the calendar breakdown treats it separately.
| Unit | Seconds |
|---|---|
| 1 minute | 60 |
| 1 hour | 3,600 |
| 1 day | 86,400 |
| 1 week | 604,800 |
| 30 days | 2,592,000 |
| 365 days | 31,536,000 |
Calendar breakdown: years, months and days
Saying a duration is '2 years, 3 months and 5 days' requires walking through real months, whose lengths vary. The calculator counts full years from the start, then full months, then days, then the remaining hours and minutes — the convention used for ages and tenancies. If the end clock time is earlier than the start's, one day is borrowed and the difference shows as hours. For pure day counts without months, the day counter is simpler.
Reading the result
The headline gives the duration in the most natural unit for its size: hours and minutes under a day, days plus hours and minutes above. The calendar line below it expresses long spans as years, months and days, which is what people mean when they say a job took 'a year and three months'. The unit list converts the whole duration into weeks, days, hours, minutes and seconds — with decimals, so 67 hours is also 2.792 days and 0.399 weeks — for spreadsheets and invoices that need a single figure.
| Unit | Value |
|---|---|
| Weeks | 0.399 |
| Days | 2.792 |
| Hours | 67 |
| Minutes | 4,020 |
| Seconds | 241,200 |
| Calendar | 2 days 19 hours |
Uses
Logging hours on a multi-day job, working out the length of a hospital stay or a rental, checking a countdown, measuring how long a process ran from its log timestamps, or settling how long ago something happened to the hour. For a single shift within one day the hours calculator is quicker; for a full week, the time card calculator.