Returns the local time hour value without the date in the form of a number from 1 through 24.
Use
HOUR(time) and replace
time with a time value or value such as TIMENOW().
Example
HOUR(TIMEVALUE(ClosedDate))
displays only the hour in a time field based on the value of the Time Closed field. HOUR(TIMEVALUE("17:30:45.125")) returns 17.