CentOS 7, PostgreSQL 12 permanently set timezone

Permanently set timezone
If you’d like to permanently change the default PostgreSQL time zone for all of your databases, you’ll need to modify the postgresql.conf file.

Find postgresql.conf file.
```
# find / -name postgresql.conf
  /var/lib/pgsql/12/data/postgresql.conf
```
Change timezone in the postgresql.conf file
```
# vi /var/lib/pgsql/12/data/postgresql.conf
  ...
  log_timezone = 'posix/Singapore'
  ...
  timezone = 'posix/Singapore'
  
  :wq
```
Restart database service after committing the change.
```
# sudo systemctl restart postgresql-12
# systemctl status postgresql-12
```

Find PostgreSQL timezone info.

Use psql to connect to a database.

# psql -h 192.168.1.x -p 5432 -U postgres -d postgres

Show timezone of the database.

postgres=# SHOW TIMEZONE
    TimeZone
--------------
 Asia/Singapore
 
postgres=# SELECT now();

Get time zone list, and get the exact name of your time zone.

SELECT * FROM pg_timezone_names where name like '%Singapore%';

         name         | abbrev | utc_offset | is_dst
----------------------+--------+------------+--------
 Asia/Singapore       | +08    | 08:00:00   | f
 posix/Asia/Singapore | +08    | 08:00:00   | f
 posix/Singapore      | +08    | 08:00:00   | f
 Singapore            | +08    | 08:00:00   | f
(4 rows)