For an ordinary overnight shift, add the time before midnight to the time after midnight. On daylight saving transition nights, use the actual date and time zone to measure elapsed time.
An ordinary overnight example
From 10:00 PM to 6:00 AM is 8 clock hours. Subtracting a 30-minute unpaid break gives 7 hours 30 minutes. The calculator marks an earlier clock-out time as +1 day so you can see the overnight assumption.
Spring forward removes an hour
In America/New_York, 1:00 AM to 4:00 AM on March 8, 2026 is 3 clock hours but only 2 actual elapsed hours. The clock skips from 1:59 AM to 3:00 AM.
Fall back repeats an hour
In America/New_York, midnight to 4:00 AM on November 1, 2026 is 4 clock hours but 5 actual elapsed hours. Times in the repeated hour, such as 1:30 AM, require an earlier or later occurrence to be identified.
Use Advanced for actual elapsed time
Set the real workweek date, enable time-zone calculation, and choose the correct zone. By default the calculator asks you to resolve skipped or repeated local times. If you choose earlier or later for a skipped time, it shifts the local time across the gap.
Check the method
Read the calculation methodology for all assumptions, precision choices, and limitations.