'Infinity' in date columns?

The documentation at
http://www.postgresql.org/docs/8.3/static/datatype-datetime.html seems to
say that the special value 'infinity' ("later than all other time stamps")
should work for an date-time column, and the type "date" is listed as among
the date-time data types.

But I can't get 'infinity' to work for columns of type "date".

Here's a test case:

CREATE TABLE _test

(

timestampx timestamp without time zone DEFAULT 'infinity'::timestamp
without time zone,

datex date DEFAULT 'infinity'::timestamp without time zone

)

);

INSERT INTO _test DEFAULT VALUES;

SELECT * FROM _test;

This returns (as viewed through pgAdmin III):

timestampx datex

----------- -----

infinity

When I tried to declared the "datex" column like this:

datex date DEFAULT 'infinity'::date

I got this:

ERROR: invalid input syntax for type date: "infinity"

Is there any way to get 'infinity' to work for a "date" column?

Or any other way to get the equivalent functionality in a date column?

~ TIA

~ Ken