FW: How to select the millisecond/microsecond parts of the dateti me column

> Hello,
>
> Product version: Postgres 6.5.3
>
> SELECT DATETIME('MILLISECOND', 'NOW'::DATETIME) always returns 0(ZERO) and
> so does 'MICROSECOND'. However a reading of the manuals indicate that the
> database supports much higher precision values. How do I retrieve the
> additional precision values (beyond seconds) when I use the datetime
> field? This is a requirement for a conversion project that I am working
> on. Could someone help please.
>
> Thanks
> Kannan
>