SQL & PL/SQL :: How To Manipulate Greater Than 24 Hour Clock In Oracle

I have an Oracle application that deals with a 29 hour clock. so the days begin at 5am instead of midnight. I am trying to get data from a table where time is up to certain number of hours, but when it reached the 00 clock my whole query returns no records, even though there is plenty of records before the midnight hour, because the data is saved as lets say 2530 instead of 0130

I am using this

SELECT *
FROM WORK.WORK_UNIT
WHERE (to_char (current_garage) = :entry_blk.curr_garage
OR 'all' = :entry_blk.curr_garage)
AND route >= 0 AND run >= 0
AND ((package_id > 0 and work_code = 99) OR
(package_id is null and work_code = 1))
and Nvl (Emp_No, 0) = 0
AND work_date = :entry_blk.p_work_date
AND on_time <= TO_CHAR(SYSDATE + :Entry_Blk.up_to_hour/24, 'HH24MI')

since oracle deals with a 24hour clock, my code doesn't seem to work if there is data for after midnight (00 hour). I am using :Entry_Blk.up_to_hour/24 to determine up to how many hours I want to see data, i.e.

on_time <= TO_CHAR(SYSDATE + 2/24, 'HH24MI')
will give me data up to 2 hours