I submitted this job with the following error on 8.1.6 on Unix.

variable jobno number;
begin
dbms_job.submit(:jobno,'trunc_table','NEXT_DAY(TRUNC(SYSDATE), ''MONDAY'') + 6/24');
COMMIT;
END;
/

I got the following error.
ERROR at line 2:
ORA-01858: a non-numeric character was found where a numeric was expected
ORA-06512: at line 2

How can I resolve this? Thanks