How to schedule a job to run the first Saturday at 6pm every month of the year ?

How to schedule a job to run the first Saturday at 6pm every month of the year ?

Is it ok for

set serveroutput on
begin
 print_dates('FREQ=MONTHLY;BYDAY=1SAT ;',
     to_timestamp_tz('01-JAN-2012 18:00:00','DD-MON-YYYY HH24:MI:SS'), 12);
end;
/

If Ok , I think print_dates code is not complete , how to do it ?

Thanks in Advance,
Dina