Migrate Data From Old To New Database

I need to migrate the data from old to new database. In the old database i have table t_emp

create table t_emp(
EMP_YYYY VARCHAR2(4 BYTE),
EMP_MM VARCHAR2(2 BYTE),
EMP_DD VARCHAR2(2 BYTE),
EMP_HH VARCHAR2(2 BYTE),
EMP_TIME_MN VARCHAR2(2 BYTE),
EMP_TIME_SS VARCHAR2(2 BYTE),
EMP_TIME_HS VARCHAR2(2 BYTE),
EMP_NO);

ex:
1998 02 23 12 01 29

now i have one more new table in new database which contains

Create table t_emp_new
(start_date date);

i need to load all the old historical data into new table using PL/SQL. How can i combine YYYY,MM,DD,HH,MN,SS,HS and insert as a single date.

02:23:1998 12:01:29