Question about PARTIAL DATE type/s

Hi,

I have text fields which contains dates in the format 'YYYYMM' (four
positions for the year, two for the month).
These fields are contained in text files which I load into the DB.

When I convert this field to a date using

to_date("PARTIAL_DATE_FIELD",'YYYYMM'); -- (a cast won't recognize
the input as valid)

I still get full dates as an output, for example,
'198801' ---> 1988-01*-01*
'196408' ---> 1964-08*-01*
and so on, what is wrong in this case because nowhere it is said that I
have the /first/ of that month, the entry just says that the event in
question happened /during/ that month.

*My question:*
Is it possible to define fields which contain partial dates per above? I
found nothing in the manual.

Thanks,

RD