get time for timezone - sql

Question

I'm hurting my head again this :
On postgresql, I would like to get the local time for a given timezone.
So, at 15:45 GMT, I want 16:45 for +01:00, but I can't get the good anwser :
SQL Fiddle
Query 1:
select current_timestamp at time zone 'GMT' as time_local_gmt
Results:
| time_local_gmt |
|-----------------------------|
| 2018-01-26T15:45:10.871659Z |
This is OK.
Query 2:
select current_timestamp at time zone '+01:00' as time_local_paris
Results:
| time_local_paris |
|-----------------------------|
| 2018-01-26T14:45:10.871659Z |
This is totally wrong, seem like it's -01:00 instead of +01:00
Edit :
See the valid answer here : https://stackoverflow.com/a/48707297/5546267

Answer 1

This worked for me.
select current_timestamp at time zone 'UTC+1';
Gave me the following result.
2018-01-26T17:00:58.773039Z
There is also a list of timezone names.
Here is an excerpt from the PostgreSQL 9.6 documentation regarding timezone names.
The view pg_timezone_names provides a list of time zone names that are recognized by SET TIMEZONE, along with their associated abbreviations, UTC offsets, and daylight-savings status.
Basically, the following query will give you the current time in Paris.
SELECT current_timestamp AT TIME ZONE 'Europe/Paris';
Good Luck!

Answer 2

For completeness (even if #Avi Abrami's answer should be what you're searching for) let's take a look at the datetime operators in the docs.
One can use the INTERVAL keyword to add hours to the stored value:
SELECT current_timestamp AT TIME ZONE INTERVAL '+02:00' AS plus_two;
Which then results in
2018-01-26T17:45:10.871659Z
(when GMT time is 2018-01-26T15:45:10.871659Z)
Section 9.9.3 AT_TIME_ZONE mentions my use of INTERVAL without any preceeding operator:
In these expressions, the desired time zone zone can be specified either as a text string (e.g., 'PST') or as an interval (e.g., INTERVAL '-08:00'). In the text case, a time zone name can be specified in any of the ways described in Section 8.5.3.

Answer 3

The documentation says:
Another issue to keep in mind is that in POSIX time zone names, positive offsets are used for locations west of Greenwich. Everywhere else, PostgreSQL follows the ISO-8601 convention that positive timezone offsets are east of Greenwich.
I guess that is your problem.

Answer 4

Ok, finally found how to !
SELECT
current_timestamp
AT TIME ZONE 'GMT'
AT TIME ZONE '+01:00'
AS time_local_paris_right;
The timestamp is UTC without TZ by default, you force it as a GMT one, and then the second AT convert it with the right offset to give you the local time for the specified time zone.
SQL Fiddle
PostgreSQL 9.6 Schema Setup:
Query 2:
select current_timestamp at time zone 'GMT' as time_local_gmt
Results:
| time_local_gmt |
|-----------------------------|
| 2018-02-09T13:44:56.824107Z |
Query 3:
select current_timestamp at time zone '+01:00' as time_local_paris_wrong
Results:
| time_local_paris_wrong |
|-----------------------------|
| 2018-02-09T12:44:56.824107Z |
Query 4:
select current_timestamp at time zone 'GMT' at time zone '+01:00' as time_local_paris_right
Results:
| time_local_paris_right |
|-----------------------------|
| 2018-02-09T14:44:56.824107Z |