BUG #1993: Adding/subtracting negative time intervals changes time zone of result

The following bug has been logged online:

Bug reference:      1993
Logged by:          Nicholas
Email address:      hb@pg.x256.org
PostgreSQL version: 8.0.3,8.0.4,8.1
Operating system:   Gentoo Linux
Description:        Adding/subtracting negative time intervals changes time
zone of result
Details:

spatula ~ # psql -U postgres
Welcome to psql 8.1beta1, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help with psql commands
       \g or terminate with semicolon to execute query
       \q to quit

postgres=# SELECT VERSION();
                                                               version
----------------------------------------------------------------------------
----------------------------------------------------------
 PostgreSQL 8.1beta1 on i686-pc-linux-gnu, compiled by GCC
i686-pc-linux-gnu-gcc (GCC) 3.3.6 (Gentoo 3.3.6, ssp-3.3.6-1.0, pie-8.7.8)
(1 row)

postgres=# SELECT NOW()-interval '1 week';
           ?column?
-------------------------------
 2005-10-17 08:52:37.355219+10
(1 row)

postgres=# SELECT NOW()-interval '-1 week';
           ?column?
-------------------------------
 2005-10-31 08:52:39.021583+11
(1 row)

postgres=#