foo=> SET TIMEZONE TO 'Japan';
SET
foo=> SELECT '2011-01-01 00:00:00'::TIMESTAMP;
      timestamp      
---------------------
 2011-01-01 00:00:00
(1 row)

foo=> SELECT '2011-01-01 00:00:00'::TIMESTAMP WITH TIME ZONE;
      timestamptz       
------------------------
 2011-01-01 00:00:00+09
(1 row)

foo=> SELECT '2011-01-01 00:00:00+03'::TIMESTAMP;
      timestamp      
---------------------
 2011-01-01 00:00:00
(1 row)

foo=> SELECT '2011-01-01 00:00:00+03'::TIMESTAMP WITH TIME ZONE;
      timestamptz       
------------------------
 2011-01-01 06:00:00+09
(1 row)

foo=> SET TIMEZONE TO 'Australia/Melbourne';
SET
foo=> SELECT '2011-01-01 00:00:00'::TIMESTAMP;
      timestamp      
---------------------
 2011-01-01 00:00:00
(1 row)

foo=> SELECT '2011-01-01 00:00:00'::TIMESTAMP WITH TIME ZONE;
      timestamptz       
------------------------
 2011-01-01 00:00:00+11
(1 row)

foo=> SELECT '2011-01-01 00:00:00+03'::TIMESTAMP;
      timestamp      
---------------------
 2011-01-01 00:00:00
(1 row)

foo=> SELECT '2011-01-01 00:00:00+03'::TIMESTAMP WITH TIME ZONE;
      timestamptz       
------------------------
 2011-01-01 08:00:00+11
(1 row)