PostgreSQL TIMESTAMPs and time zones

timezones.sql

james=> SHOW TimeZone;
     TimeZone     
------------------
 America/New_York
(1 row)

james=> CREATE TEMPORARY TABLE test (t TIMESTAMP WITH TIME ZONE);
CREATE TABLE
james=> INSERT INTO test VALUES ('2020-03-20 12:30:00 America/New_York'), ('2020-03-20 15:30:00 Europe/London');
INSERT 0 2

james=> SELECT * FROM test;
           t            
------------------------
 2020-03-20 12:30:00-04
 2020-03-20 11:30:00-04
(2 rows)


james=> SET TIME ZONE 'UTC';
SET
james=> SELECT * FROM test;
           t            
------------------------
 2020-03-20 16:30:00+00
 2020-03-20 15:30:00+00
(2 rows)