Well, I still think SYSDATE is a perfect example of DATE datatype. Scalar datatypes are defined in very exact way in Oracle, there is no such type as "other" type . Anyway, of what datatype is the following expression?

to_date('01.01.2001','dd.mm.yyyy')

Another perfect example of DATE datatype, I would say. And it has nothing to do with system clock this time. So how come VSIZE() again returns 8 for it?

SQL> select vsize(to_date('01.01.2001','dd.mm.yyyy')) from dual;

VSIZE(TO_DATE('01.01.2001','DD.MM.YYYY'))
-----------------------------------------
8