Truncate Clock Time
Round a clock time down to a clear interval while keeping midnight rollover and the original day boundary visible.
A QUICK WALKTHROUGH
How to use this tool
- Enter a 24-hour clock time in HH:MM:SS format.
- Choose the interval to truncate toward the start of the day.
- Review the truncated time and copy it for a schedule, query, or report.
Downward truncation is explicit
The tool always moves toward 00:00:00 on the same day. A 15-minute interval maps 10:14:59 to 10:00:00 and 10:15:00 to 10:15:00; it never rounds up to the next interval.
Clock values stay local
Input is a wall-clock value with no date or time zone. The result is formatted as HH:MM:SS, and the page runs validation, calculation, and copying entirely in your browser.
GOOD TO KNOW
Common questions
What happens at midnight?
Any valid time from 00:00:00 through the first interval boundary truncates to 00:00:00. The result never rolls back to the previous date.
Can I use a custom interval?
Yes. Choose Custom and enter a whole number of minutes from 1 to 1,440. Intervals longer than one day still produce the day start.
Does the tool change the date?
No. It accepts and returns only a clock time, and truncation always stays on that same clock day.