SQL & PL/SQL :: Calculate Post Arrival Date

Find the sample data and table.

CREATE TABLE table_x
( arrival_time VARCHAR2 (8),
post_arrival_time VARCHAR2 (8),
arrival_date date
);
INSERT INTO table_x VALUES ('3:50 PM', '3:50 AM',trunc(sysdate)); -- Post arrival date = trunc(sysdate) - 1
INSERT INTO table_x VALUES ('3:50 AM', '1:00 AM',trunc(sysdate)); -- Post arrival date = trunc(sysdate)
INSERT INTO table_x VALUES ('11:59 AM','11:59 PM',trunc(sysdate)); -- Post arrival date = trunc(sysdate) - 1

Need to calculate Post arrival date .. which will be always < = Arrival date