Sets the time zone used for timestamps written in the server log. Unlike TimeZone, this value is cluster-wide, so that all sessions will report timestamps consistently. The built-in default is
GMT, but that is typically overridden in postgresql.conf; initdb will install a setting there corresponding to its system environment. See datatype-timezones for more information. This parameter can only be set in the postgresql.conf file or on the server command line.
To avoid confusion, it's often useful to log to the timezone where the DBA or sysadmin lives.