Any reason why postgres can't detect time zone on my machine automatically?

LOG:  could not recognize system timezone, defaulting to "Etc/GMT-8"
HINT:  You can specify the correct timezone in postgresql.conf.
postmaster starting
-bash-2.05b$ LOG:  database system was shut down at 2004-05-31 15:19:00 
GMT-8
LOG:  checkpoint record is at 0/A47C80
LOG:  redo record is at 0/A47C80; undo record is at 0/0; shutdown TRUE
LOG:  next transaction ID: 536; next OID: 17218
LOG:  database system is ready


-bash-2.05b$ date
Mon May 31 15:21:10 WST 2004

Mon, 31 May 2004 15:21:57 +0800
Christopher Kings-Lynne <chriskl@familyhealth.com.au>
Can't detect time zone