FND_Request.submit_request Questoin

Need helping in correcting the Date format. I'm trying to submit Purge sign on audit data program from backend . Here is the code that i've pasted but not completly . The one indicated in bold is the problematic one . I'd retain the last 4 days old data and purge the old data thats why i said sysdate-4 it works for the first time and for sub-sequent runs with its regular schedule its not working which means parameters will be null .

Can anybody correct me where i'm doing wrong.

fnd_request.submit_request

                      (application => 'FND'


                       ,program     => 'FNDSCPRG'

                       ,start_time  => sysdate --

to_char(sysdate,'DD-MON-YYYY') || ' 19:30:00'
        * ,argument1   => to_char(sysdate-4,'YYYY-MON-DD HH24:MI:SS')*
         ,argument2 => chr(0)
                       );

Regards
Bala

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