SQL & PL/SQL :: How To Compare Hours

I want to write a function that gets:

1. event_date (dd/mm/yyyy)
2. event_start_time (??/??/???? HH24:MI)
3. event_end_time (??/??/???? HH24:MI)

I got a table called EVENTS that got 2 fields:

1. event_date (dd/mm/yyyy HH24:MI)
2. event_end_date (??/??/???? HH24:MI)

and want to check if there is an event in my EVENTS table that occurs in the same dd/mm/yyyy as the input, and can disturb the input event times. means:

input.event_start_time is between EVENTS.event_date
and EVENTS.event_end_date
and
input.event_end_time is between EVENTS.event_date
and EVENTS.event_end_date

but to compare only the hours here! (HH24:MI)
because the date (dd/mm/yyyy) is checked before..

I don't know how to cut only the hours out of the date and compare them, and don't know how to write the whole function.