HOUR() returns the hours portion of a specified DateTime as a number.
Use HOUR() to isolate the hours portion of a DateTime.
HOUR(D)
HOUR() returns a numeric value denoting the hours portion of a DateTime.
If the DateTime is purely a date, then HOUR() returns a zero value.
Using a 24-hour clock and a time of 11:12:32 p.m.:
HOUR(‘23:12:32‘) = 23