Time Duration Calculator
Measure elapsed time between two clock times or datetimes in clear units. Results use exact seconds and show days, hours, minutes, and seconds.
Worked examples
Example 1
9:15 AM to 5:45:30 PM
On the same day this is 8 hours, 30 minutes, 30 seconds, or 30,630 total seconds.
Example 2
10:30 PM to 6:15 AM the next day
With the next-day option selected, the duration is 7 hours, 45 minutes. Without that option, an earlier end time is rejected.
Example 3
31 January to 1 March 2024 at noon
The calendar span is 30 days. February 2024 has 29 days, so the result is not based on equal 30-day months. Adding 7 hours 45 minutes to 10:30 PM lands at 6:15:00 AM, 1 day later.
Common questions
Why is an earlier end time not counted as overnight automatically?
A clock time alone does not say which day it belongs to. If the end is earlier than the start, select “End time is on the next day.” Otherwise the calculator asks you to confirm the overnight span instead of guessing.
Do multi-day results change for daylight saving?
No. Each calendar day counts as exactly 24 wall-clock hours, or 86,400 seconds. A local clock that skips or repeats an hour during a daylight-saving change is not given a different elapsed-time adjustment.
How can the total hours stay exact?
The duration is stored as a whole number of seconds. Total hours or minutes are shown as a short decimal only when that division ends evenly. Otherwise the result stays in whole hours, minutes, and seconds so it is not rounded.