Forked from: corbanb/gist:76d0658493e93830af48 which borrowed heavily from http://blog.shupp.org/2012/08/12/local-timezone-lookups-by-coordinates-with-postgis/ to make this geared towards mac users, which has been updated.
$ psql -U <user> -d template_postgis
$ template_postgis=> select postgis_lib_version(); should return installed version!
$ template_postgis=> \d+tz_world