Defaulting to current date

I want to have a field with a date/time value that defaults to the time the
record was inserted.  I also want to be abled to index this field.

If I create with:
create table test
(
Date timestamp not null default CURRENT_TIMESTAMP
);

The default value works as expected but I cannot create an index:

create index testidx on test (Date);
ERROR:  Can't find a default operator class for type 1296.

I have also tried to create the field as a DATETIME field.
create table test
(
Date datetime not null default CURRENT_TIME
);

I can create the index but the field defaults to the table creation time
instead of the insertion time.
I have tried several syntax variations using CURRENT_DATE, CURRENT_TIME,
CURRENT_TIMESTAMP, 'now', and text 'now'.  The last one is suggested in the
online documentation, however they refer specifically to v6.4 and I am
running 6.3.2.

It seems like I can index the field or used a default value but not both.
Is this true?

Bryan White
ArcaMax Inc.
Yorktown VA
www.arcamax.com