Você sempre pode tentar:
SQL> select to_timestamp( '9999-12-31 23:59:59', 'yyyy-mm-dd hh24:mi:ss' ) from dual;
TO_TIMESTAMP('9999-12-3123:59:59','YYYY-MM-DDHH24:MI:SS')
---------------------------------------------------------------------------
31-DEC-99 11.59.59.000000000 PM
e:
SQL> select to_timestamp( '9999-12-31 23:59:59', 'yyyy-mm-dd hh24:mi:ss' )+1 from dual;
select to_timestamp( '9999-12-31 23:59:59', 'yyyy-mm-dd hh24:mi:ss' )+1 from dual
*
ERROR at line 1:
ORA-01841: (full) year must be between -4713 and +9999, and not be 0
