Time Duration Calculator

A time duration is the end time minus the start time, across as many days as it takes.

Duration = end date and time − start date and time

The calculator puts both moments on one timeline and subtracts. The answer comes four ways: hours and minutes, days, hours and minutes, decimal hours and total minutes. Because each time carries its own date, a span can run past midnight, past a weekend or past a month end without any guessing about which day the end belongs to. If the end comes before the start, the calculator counts from the earlier one and says so.

The time zone menu decides how long a day is. With a US zone picked, the calculator follows that zone's daylight saving rules, so a span that crosses a clock change comes out an hour longer or shorter. With “No time zone” every day is exactly 24 hours, which is plain clock arithmetic.

Monday at 10:00 PM to Wednesday at 6:30 AM is 32 hours and 30 minutes.

Those are the times the calculator opens with: an invented on-call stretch in Eastern time that starts on Monday, November 2, 2026 at 10:00 PM and ends on Wednesday, November 4 at 6:30 AM.

• Monday, 10:00 PM to midnight: 2 hours
• Tuesday, midnight to midnight: 24 hours
• Wednesday, midnight to 6:30 AM: 6 hours 30 minutes
• Total: 32 hours 30 minutes, which is 1 day, 8 hours and 30 minutes
• In decimal hours: 32 + 30 ÷ 60 = 32.5, or 1,950 minutes

No clock change falls inside this stretch, because in 2026 the clocks go back on Sunday, November 1, the day before it starts. Switch to “Add or subtract” and the same start runs the other way: 8 hours 30 minutes after Monday at 10:00 PM is Tuesday, November 3 at 6:30 AM.

Two days a year are not 24 hours long in most of the United States.

Federal law, 15 U.S.C. 260a, moves standard time forward an hour from 2 a.m. on the second Sunday of March to 2 a.m. on the first Sunday of November. NIST, the national timekeeper, gives the 2026 dates as March 8 and November 1. On March 8 the local time skips from 2 a.m. to 3 a.m., “so there is one less hour in that day.” On November 1, 2 a.m. becomes 1 a.m. again “and that hour is repeated.” Midnight to midnight, the first day lasts 23 hours and the second 25.

NIST puts daylight saving time at 238 days, about 65% of the year. The same rule sets the 2027 changes for March 14 and November 7. Hawaii, Puerto Rico, the Virgin Islands, Guam, American Samoa and most of Arizona keep standard time all year, so picking Arizona or Hawaii in the menu gives 24-hour days every day.

The change nights also create clock times that do not exist or happen twice. 2:30 AM on March 8, 2026 never appears on a clock in Eastern time, so the calculator reads it as 3:30 AM and says so. 1:30 AM on November 1 happens twice, and the calculator uses the first one, still on daylight time, and names it under the result.

The night the clocks go back, an eight-hour overnight shift is nine hours of work.

The Department of Labor's Hours Worked Advisor uses a shift that starts at 11:00 p.m. and ends at 7:30 a.m. the next day with a 30-minute lunch, eight hours of work. On the night daylight saving time begins, the employee works 7 hours. On the night it ends, the hour from 1:00 a.m. to 2:00 a.m. is worked twice, so the shift is 9 hours. The Department's rule is plain: “The FLSA requires that employees must be credited with all of the hours actually worked.”

The calculator gets the same answer. From Saturday, October 31, 2026 at 11:00 PM to Sunday, November 1 at 7:30 AM in Eastern time it shows 9 hours 30 minutes on the clock, which is 9 hours after the lunch. From March 7 to March 8 it shows 7 hours 30 minutes. With “No time zone” both nights show 8 hours 30 minutes, which is the schedule rather than the hours worked. This matters to more people than it seems: the BLS found that 14.8% of wage and salary workers usually worked something other than a regular daytime schedule in 2024 and 2025, and 3.4% worked nights. The time card calculator adds up a week of such shifts.

A workweek under federal law is a fixed block of 168 hours.

Overtime is counted per workweek, and 29 CFR 778.105 defines one as “a fixed and regularly recurring period of 168 hours,” or “seven consecutive 24-hour periods.” It “need not coincide with the calendar week but may begin on any day and at any hour of the day,” and once set it stays fixed whatever hours are worked.

A workweek that starts on Monday, November 2, 2026 at 10:00 PM ends 168 hours later, on Monday, November 9 at 10:00 PM, which is what the calculator shows when you add 168 hours or 7 days to that start. The worked example's on-call stretch takes up the first 32.5 hours of that week, about 19% of it. Once the hours worked in a workweek pass 40, the overtime calculator works out time and a half.

Decimal hours turn a duration into something payroll can multiply.

Minutes are sixtieths of an hour, so 32 hours 30 minutes is 32.5 hours, not 32.30. At an invented rate of $20 an hour the right figure pays $650.00 and the wrong one $646.00, a gap of 12 minutes of pay. The hours calculator has a full table of minutes in decimal, and works one shift at a time with an unpaid break taken off.

Midnight needs care at either end of a span. NIST's times of day FAQ says “12 a.m. and 12 p.m. are ambiguous and should not be used,” and suggests 11:59 p.m. or 12:01 a.m. for deadlines. The military time converter writes the same moment as 0000 or 2400. For whole days rather than hours, the days between dates calculator counts them and the date calculator adds them to a date. When the start and the end are in different time zones, convert one into the other first with the time zone converter.

A duration shows how long someone worked, not how long they will stay.

Every number on this page measures time already spent: a shift, an on-call stretch, a workweek. None of them says who on the team is about to stop spending it with you. TeamPredict works on that part, reading public LinkedIn signals to flag resignation risk early, so the first sign of a departure is a warning while there is still time to talk, rather than a rota with a gap in it.