BUG #13691: Postgres reverse timezone system

The following bug has been logged on the website:

Bug reference: 13691
Logged by: Đặng Minh Dũng
Email address: dungdm93(at)live(dot)com
PostgreSQL version: 9.4.4
Operating system: Microsoft Windows 7
Description:

I'm in Vietnam with timezone ICT (GMT+7).
I wanna find the best way to convert datetime between timezone like this:

postgres=# SELECT
postgres-# now() AS "NOW",
postgres-# now() AT TIME ZONE 'ICT' AS "ICT",
postgres-# now() AT TIME ZONE '+7:00' AS "+7:00",
postgres-# now() AT TIME ZONE 'UTC+7' AS "UTC+7",
postgres-# now() AT TIME ZONE 'UTC+7:00' AS "UTC+7:00",
postgres-# now() AT TIME ZONE 'GMT+7:00' AS "GMT+7:00";
-[ RECORD 1 ]------------------------
NOW | 2015-10-21 09:55:50.631+07
ICT | 2015-10-21 09:55:50.631
+7:00 | 2015-10-20 19:55:50.631
UTC+7 | 2015-10-20 19:55:50.631
UTC+7:00 | 2015-10-20 19:55:50.631
GMT+7:00 | 2015-10-20 19:55:50.631

As you can see, ICT and GMT+7:00 or +7:00 are identical, Unfortunately, the
query results are different. However, when i select:

SELECT now() AT TIME ZONE '-7:00' AS "-7:00";

The result is correct. So why Postgres reverse timezone system???
Thanks you.