postgres time zone settings

Hai all,

when i was going through the Postgresql documents, i came across a section which tells about the TIME ZONE settings


what i understood from the document is, based on the value given in this conf file postgres will add or subtract the displacement hours to the system time assuming that the system time is the GMT.
so there should be a configuration settings which will tell the postgres that the displacement is zero.
How I can set the displacement is zero?

Thanks in advance
Anoop