why my query is not using index??

postgres=# explain ANALYZE select * from test where today < '2004-01-01';
                                             QUERY PLAN
----------------------------------------------------------------------------------------------------
 Seq Scan on test  (cost=0.00..19.51 rows=334 width=44) (actual
time=0.545..2.429 rows=721 loops=1)
   Filter: (today < '2004-01-01 00:00:00'::timestamp without time zone)
 Total runtime: 3.072 ms
(3 rows)

postgres=# explain ANALYZE select * from test where today > '2003-01-01'
and today < '2004-01-01';
                                                                  QUERY
PLAN

-----------------------------------------------------------------------------------------------------------------------------------------------
 Index Scan using idx_today on test  (cost=0.00..18.89 rows=6 width=44)
(actual time=0.055..1.098 rows=365 loops=1)
   Index Cond: ((today > '2003-01-01 00:00:00'::timestamp without time
zone) AND (today < '2004-01-01 00:00:00'::timestamp without time zone))
 Total runtime: 1.471 ms
(3 rows)

hello

I was expected 1st query should using index, but it doesn't
2nd query doing perfect as you see.

can you explain to me why it's not doing that i expected??
now I'm currently using postgresql 8.0pre3 on linux

/hyunsung jang.