set enable_seqscan=off;
CREATE TABLE test_timestamptz (
	i timestamptz
);
INSERT INTO test_timestamptz VALUES
	( '2004-10-26 03:55:08' ),
	( '2004-10-26 04:55:08' ),
	( '2004-10-26 05:55:08' ),
	( '2004-10-26 08:55:08' ),
	( '2004-10-26 09:55:08' ),
	( '2004-10-26 10:55:08' )
;
CREATE INDEX idx_timestamptz ON test_timestamptz USING gin (i);
SELECT * FROM test_timestamptz WHERE i<'2004-10-26 08:55:08'::timestamptz ORDER BY i;
              i               
------------------------------
 Tue Oct 26 03:55:08 2004 PDT
 Tue Oct 26 04:55:08 2004 PDT
 Tue Oct 26 05:55:08 2004 PDT
(3 rows)

SELECT * FROM test_timestamptz WHERE i<='2004-10-26 08:55:08'::timestamptz ORDER BY i;
              i               
------------------------------
 Tue Oct 26 03:55:08 2004 PDT
 Tue Oct 26 04:55:08 2004 PDT
 Tue Oct 26 05:55:08 2004 PDT
 Tue Oct 26 08:55:08 2004 PDT
(4 rows)

SELECT * FROM test_timestamptz WHERE i='2004-10-26 08:55:08'::timestamptz ORDER BY i;
              i               
------------------------------
 Tue Oct 26 08:55:08 2004 PDT
(1 row)

SELECT * FROM test_timestamptz WHERE i>='2004-10-26 08:55:08'::timestamptz ORDER BY i;
              i               
------------------------------
 Tue Oct 26 08:55:08 2004 PDT
 Tue Oct 26 09:55:08 2004 PDT
 Tue Oct 26 10:55:08 2004 PDT
(3 rows)

SELECT * FROM test_timestamptz WHERE i>'2004-10-26 08:55:08'::timestamptz ORDER BY i;
              i               
------------------------------
 Tue Oct 26 09:55:08 2004 PDT
 Tue Oct 26 10:55:08 2004 PDT
(2 rows)