how do I filter the time field in oracle

I have a table

Schedule
------------
id int
mydate date
starttime date
endtime date

What I actually required is the mydate (18-Jan-2004), starttime( 05:00 pm), endtime (06:00 pm).

I am storing the data as follow:

mydate 18-Jan-2004 12:00:00 AM
starttime 18-Jan-2004 05:00:00 PM
endtime 18-Jan-2004 06:00:00 PM

Is there a better way to store these information?

Say I current machine time (not the server time) is 04:00 PM and I would like to use this information to find id which starttime is later than 04:00 PM. Should I use to_date or is there a better way to construct the SQL statement?

Thank you.

Have you tried using the `interval 'n' ` function?
where current_date > sysdate + interval '4' hour;