Round Unix to Hour
Enter a Unix timestamp in seconds and get the UTC hour boundary at or before it.
Enter a finite Unix timestamp in seconds.
A QUICK WALKTHROUGH
How to use this tool
- Enter a finite Unix timestamp in seconds.
- Floor it to a UTC hour boundary.
- Copy the integer timestamp and ISO UTC result.
UTC floor
The result is floor(timestamp / 3600) × 3600, so minutes and seconds are removed in UTC.
Negative seconds are mathematical floor
Negative values use mathematical floor, not truncation toward zero. For example, -1 becomes -3600, representing 1969-12-31T23:00:00.000Z.
Input limits
Enter a finite decimal number of Unix seconds within the browser Date range. Invalid, blank, or non-finite input is rejected.
GOOD TO KNOW
Common questions
Does it round to the nearest hour?
No. It always floors to the UTC hour at or before the input.
How are negative timestamps handled?
They use mathematical floor; -1 seconds becomes -3600 seconds.
Are milliseconds accepted?
The input is Unix seconds and may be fractional; the output is an integer whole-second hour boundary.