Usually people say 5 to 8 - not 5 to 8 o'clock and NOT 5 of 8 o'clock.
More common is digital format e.g 7:50
To say 7 o'clock, you say, Il est sept heures. To say 8 o'clock, you say, Il est huit heures.
Son las ocho en punto
Nuestra casa. A las ocho.
It is short for "of the clock".
They say, 8 o clock is the latest that they will meet.
obtuse
14 Seconds
5 o clock or 6 o clock
There are 2 hours between 3 and 5 o'clock.
2000 hrs
It is a obtuse angle.
8:00