Dates & time
Add duration to a clock time
Add or subtract seconds and keep track of midnight crossings.
A clear answer. Here’s how.
Parses a 24-hour starting clock with hours 00–23 and minutes/seconds 00–59. Adds a signed whole-second duration, reports a normalised HH:MM:SS and signed day carry using floor division. This is fixed 24-hour arithmetic without dates, leap seconds, time zones or daylight-saving rules.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Starting clock time (HH:MM or HH:MM:SS)
- 23:30
- Seconds to add (negative to subtract)
- 5400
Example result
- Result clock
- 01:00:00
- Signed day carry
- 1