Measure exact elapsed time between two moments - days, months, years, leap years, and time of day included.
The end moment must be at or after the start moment. Leap years and month lengths are handled automatically.
Elapsed time-
Total days:-
Total hours:-
Total minutes:-
Total seconds:-
Pick a start and an end moment to measure the time between them.
Add / Subtract Date & Time
Start from any date and time, add or subtract a duration, and read the resulting date and time. The elapsed-time calculator above stays available.
Whole numbers of 0 or more. Adding 90 minutes moves the clock forward by 1 hour and 30 minutes; midnight, month, year, and leap-day boundaries are handled automatically.
Resulting date and time-
Applied duration:-
Pick a starting date and time, choose Add or Subtract, enter a duration, then calculate.
Quick Guide
Measure elapsed time between two moments
Step 1: Choose the starting moment with the date and time picker
Step 2: Choose the ending moment, later than the start
Step 3: Click Calculate Elapsed Time
Step 4: Read the calendar breakdown and the total days, hours, minutes, and seconds
Example: From 2026-01-01 09:00 to 2026-01-03 14:30 the result is 0y 0m 2d 5h 30m 0s - 2 days, 5 hours, 30 minutes.
Add or subtract from a date and time
Step 1: Keep or edit the starting date and time - it is prefilled with the current moment
Step 2: Choose Add or Subtract under Operation
Step 3: Enter the duration in days, hours, minutes, and seconds (whole numbers of 0 or more)
Step 4: Click Calculate Resulting Date and Time and read the resulting date, time, and applied duration
Date & Time Duration Calculator answers the question "how much time passed between these two moments?" for any pair of date-and-time inputs. Unlike a plain date-difference tool, it includes the time of day, so a span from Monday 09:00 to Wednesday 14:30 shows as calendar units and as exact hour totals. Because the math uses real UTC calendar dates, durations that cross 29 February, a 30-day month, or a year boundary stay exact. See also: the time duration calculator for clock times alone or the date difference calculator for whole dates.
How It Works
Both moments are parsed into UTC timestamps, so daylight-saving changes in your local zone cannot shift the answer. The exact difference in seconds is converted into total days, hours, and minutes. For the calendar breakdown, the calculator walks forward from the start - whole years first, then whole months, clamped to the real length of each month - and reports whatever days, hours, minutes, and seconds remain. The end moment must be at or after the start; otherwise a validation message appears.
Use Cases
Track project or contract periods from kickoff to delivery down to the second
Count the time between two log entries, releases, or scheduled events
Verify durations that span leap days, month ends, or new-year boundaries
Frequently Asked Questions
What is a date and time duration?
It is the exact elapsed time between one date-and-time moment and another. This calculator reports it two ways: as a calendar breakdown of years, months, days, hours, minutes, and seconds, and as totals in days, hours, minutes, and seconds.
Does this calculator handle leap years correctly?
Yes. All arithmetic runs in UTC on real calendar dates, so 29 February is counted in leap years and skipped otherwise, and month lengths are respected whenever the duration crosses a month or year boundary.
What happens if the end time is before the start time?
The calculator shows a validation message instead of a result. Enter the earlier moment as the start and the later moment as the end, and the duration will be computed accurately.
How do I add or subtract time from a date and time?
Use the Add / Subtract Date & Time panel below the calculator: keep or edit the starting date and time (it is prefilled with the current moment), choose Add or Subtract, enter whole days, hours, minutes, and seconds, then press Calculate Resulting Date and Time. The result shows the new date and time together with the duration that was applied.
How are midnight, month-end, and leap-year boundaries handled?
Elapsed-time math runs in UTC on real calendar dates, so month lengths and 29 February resolve correctly. Date shifts move whole seconds from the starting moment, so crossing midnight, a month end, or a leap day is automatic - 2026-03-31 23:45:10 plus 1d becomes 2026-04-01 23:45:10.
What happens if a required field is empty or invalid?
A validation message appears instead of a result - for example, the calculator asks for both a start and an end moment, for the end to be at or after the start, or for whole numbers of 0 or more in the duration fields. Correct the input and calculate again.