ORA-01841: Creation of dates bc

It took me some time to find out what the problem of the following statement is. Ok, I did not try too hard at it 🙊.

select to_date('-0001-01-01', 'YYYY-MM-DD') from DUAL;

It simply misses the sign sign 😉.

select to_date('-0001-01-01', 'SYYYY-MM-DD') from DUAL;