我有一个TIMESTAMP WITHOUT TIME ZONE类型的列，并希望默认为UTC的当前时间。获取当前时间在UTC是很容易：
postgres=# select now() at time zone 'utc';
timezone
----------------------------
2013-05-17 12:52:51.337466
(1 row)
正在使用列的当前时间戳：
postgres=# create temporary table test(id int,ts timestamp without time zone default current_timestamp);
CREATE TABLE
postgres=# insert into test values (1) returning ts;
ts
----------------------------
2013-05-17 14:54:33.072725
(1 row)
但这使用本地时间。试图强制到UTC导致语法错误：
postgres=# create temporary table test(id int,ts timestamp without time zone default now() at time zone 'utc'); ERROR: Syntax error at or near "at" LINE 1: ...int,ts timestamp without time zone default now() at time zo...
