Time Duration Calculator

Calculate the time between two times

Enter a start and end time, including seconds when needed. The result shows the interval as days, hours, minutes, and seconds, then gives equivalent totals in hours, minutes, and seconds. The browser may display an AM/PM control or a 24-hour clock according to your locale; both represent the same calculation.

seconds after midnight = hours x 3,600 + minutes x 60 + seconds

duration = end seconds - start seconds; add 86,400 when the end time is earlier and no dates are entered

Overnight intervals and identical times

In Two times mode, an end time earlier than the start is treated as the following day. For example, 10:00 PM to 6:00 AM is 8 hours, or 28,800 seconds. The result identifies this next-day assumption so it is visible rather than silently changing your inputs.

The same start and end time represents zero elapsed time in this mode. To calculate a full 24-hour day or an interval spanning several days, choose Two dates and times and enter the actual dates. The calculator does not assume an extra day when both clock values are identical.

Time between two dates

Date mode combines each calendar date with its time of day and subtracts the start from the end. It uses the Gregorian calendar, including leap years and different month lengths. An end date and time before the start produces an input message; use the swap control if you entered the two endpoints in reverse order.

For example, January 1 at 8:30 AM through January 2 at 5:30 PM is 1 day and 9 hours. That is 33 total hours, 1,980 total minutes, or 118,800 seconds. February 28 through March 1 spans two days in a leap year and one day in a non-leap year when the times of day match.

Decimal hours are different from hours and minutes

Divide total seconds by 3,600 to convert a duration to decimal hours. A duration of 1 hour and 30 minutes is 1.5 hours, not 1.30 hours. Likewise, 1 hour, 0 minutes, and 20 seconds equals 3,620 seconds, about 60.333333 minutes, or 1.005556 hours. Displayed decimal totals are rounded, while the component result preserves the entered whole seconds.

total hours = total seconds / 3,600; total minutes = total seconds / 60

Clock time, time zones, and daylight saving

This tool measures the difference on one shared clock. It treats each calendar day as 24 hours and does not apply geographic time zones, daylight-saving transitions, or leap seconds. A real trip across time zones or a shift spanning a daylight-saving change can have a different physical elapsed time. For those situations, first convert both endpoints to the same UTC timeline using a time-zone-aware service.

Choose the right related tool

Use the date calculator for a difference in whole calendar days, the age calculator for age in calendar years, months, and days, or the hours calculator to add entered hours and minutes and apply an hourly rate. A duration is not automatically a paid-work total: unpaid breaks, rounding policies, overtime, and payroll rules are not applied here.

If you already have a total duration rather than two endpoints, use the seconds to hours converter for decimal hours and a component hours-minutes-seconds breakdown.

Frequently asked questions

Is 12 AM midnight or noon?

12 AM is midnight and 12 PM is noon in a 12-hour display. In a 24-hour display, use 00:00 for midnight and 12:00 for noon.

Can I include seconds?

Yes. Both time inputs accept seconds from 00 through 59. The calculation does not round to a whole minute.

Does date mode include the entire end day?

No. It stops at the exact end time you enter. Midnight on the next day is the end of a full day that began at midnight.

What does Now use?

Now fills that endpoint with the date and time reported by your device. In time-only mode, its date is retained for use if you switch to date mode.