date_part/extract parse curiosity

Hi,

I noticed that
select date_part('millennium', now()); --> 3

will execute also, unperturbed, in this form:
select date_part('millennium xxxxx', now()); --> 3

By the same token

select extract(millennium from now()) --> 3
select extract(millenniumxxxxxxxxx from now()) --> 3

This laxness occurs in all releases, and with 'millennium',
'millisecond', and 'microsecond' (at least).

Even though it's not likely to cause much real-life headaches, and I
hesitate to call it a real bug, perhaps it would be better if it could
be a bit stricter.

Thanks,

Erik Rijkers