Time zone 'GMT+8'

From http://www.postgresql.org/docs/current/static/datatype-datetime.html#DATATYPE-TIMEZONES

Another issue to keep in mind is that in POSIX time zone names,
positive offsets are used for locations west of Greenwich.

there are 3 terms which refer to GMT
GMT in the UK
Zulu time for aviators
UTC for Scientific measurements

UTC is now replacing 'Zulu' and 'GMT' for 0 time references

http://wwp.greenwichmeantime.com/info/zulu.htm
Martin Gainty
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Date: Sun, 29 Nov 2009 15:08:01 +0800
From: seiliki@so-net.net.tw
To: pgsql-general@postgresql.org
Subject: [GENERAL] Time zone 'GMT+8'

The target pgsql is compiled from 8.4rc1. 'GMT+8' can be found in installed binary file .../share/postgresql/timezone/Etc/GMT+8.

This is the recorded script:

-----BEGIN record----------
db1=# select now();
now
-------------------------------
2009-11-29 14:44:37.322414+08
(1 row)

db1=# set timezone to 'GMT+8';
SET
db1=# select now();
now
-------------------------------
2009-11-28 22:45:03.397545-08
(1 row)

db1=# set timezone to GMT-8';
SET
db1=# select now();
now
-------------------------------
2009-11-29 14:45:39.160701+08
(1 row)

db1=# set timezone to '0';
SET
db1=# select now();
now
-------------------------------
2009-11-29 06:45:54.347482+00
(1 row)
-----END record----------

I thought time zone 'GMT+8' was '8' or UTC+8, and 'GMT-8' was '-8' or UTC-8. Does the original time zone settings shipped with source have special interpretation that is different from my understanding?

Regards,
CN

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silly8888 <silly8888@gmail.com> writes:

From http://www.postgresql.org/docs/current/static/datatype-datetime.html#DATATYPE-TIMEZONES

Another issue to keep in mind is that in POSIX time zone names,
positive offsets are used for locations west of Greenwich.

Yeah, we're caught between two incompatible conventions :-(. I suggest
reading the whole section linked to above, it should make things
clearer.

regards, tom lane