Written by Sarah Mitchell · Reviewed by Alex Chen · July 15, 2026
Calculate the exact duration between two dates and times — days, hours, minutes, and seconds.
Select dates and click Calculate.
A duration is the amount of time that elapses between two moments, and unlike a clock reading it has no fixed position on the calendar. This tool computes that gap down to the second and then re-expresses it in whatever units are most convenient for you. The arithmetic happens entirely in your browser, so the timestamps you type into the fields never travel over the network.
Imagine a trip that starts on Friday, June 5, 2026, at 9:15 in the morning and ends on Monday, June 8, 2026, at 2:30 in the afternoon. From June 5 to June 8 is three full days. From 9:15 to 14:30 on the final day adds 5 hours and 15 minutes, so the complete span is 3 days, 5 hours, and 15 minutes. Expressed in smaller units the same gap is 77 hours and 15 minutes, 4,635 minutes, or 278,100 seconds, and the output shows every one of those totals next to the broken-down figure.
The most common mistake in hand-written time math is forgetting that a span crossing midnight gains hours, not loses them. A shift that starts at 10 p.m. and ends at 6 a.m. the next morning is 8 hours, and the calculator handles that boundary without you having to add twelve or subtract anything. The same logic applies to spans that cross months, leap days, and daylight-saving transitions, because the tool works from the actual calendar rather than from a fixed 24-hour assumption.
The output distinguishes between a broken-down breakdown, like 2 weeks and 3 days, and a single-unit total, like 408 hours. They describe the same span from different angles: the breakdown is what you would say aloud, while the totals are what you would feed into a billing system or a timesheet. To check the example above, multiply 3 days by 24, add 5, and keep the 15 minutes, which confirms the 77 hour and 15 minute figure.
Always double-check the 12-hour versus 24-hour display when you read the pickers, because 3 p.m. and 3 a.m. produce wildly different answers for the same day. If you leave the end time untouched, it defaults to the moment you loaded the page, which is convenient for countdown-style questions such as how long until a deadline. Seconds are included in the span and in the totals, so even sub-minute precision work can be verified.
Nothing you enter is uploaded, logged, or stored. The date pickers and the math run locally, so you can work on confidential scheduling data or personal milestones with the tab open and the network unplugged. Closing the page simply discards the inputs, which makes repeated quick checks effortless because there is no saved state to clear.
A quick mental rehearsal catches typos before they reach a schedule. Take the total hours, divide by 24, and the quotient is the days while the remainder is the leftover hours; the tool's breakdown should match that division exactly. When a span crosses midnight, an even simpler check is to count the hours from the start until midnight, add the hours from midnight until the end, and compare the sum with the reported figure.
Contractors often round partial hours up to the nearest quarter hour before invoicing, so a job that ran 5 hours and 9 minutes becomes 5.25 billable hours, while other clients expect exact minutes. Either convention is legitimate, but mixing them produces invoices that disagree with the source timesheets. For payroll and legal work, keep the raw start and end timestamps on record, because the span alone cannot prove when the work actually happened.
Because the calculator compares calendar timestamps, the answer depends on the time zone where the clock lives. A flight from New York to London departs at 10 p.m. local and arrives at 10 a.m. local, yet the journey is longer than twelve hours once the five-hour offset and the direction of travel are counted. Daylight-saving changes, which move clocks by an hour on fixed weekends, shift any span that crosses the switch date. UTC timestamps avoid that ambiguity entirely, which is why schedules exchanged between systems almost always carry the trailing Z that marks coordinated universal time. Shipping quotes, SLA windows, and project milestones are all durations, and each industry applies its own convention for what counts as a business day.