adding time zone files to the time GUI interface

[Chris Henderson]

There are many time zone files accessible from the command line
(/usr/share/zoneinfo) that don't show up in the GUI
("system-config-date"). How do I add these time zones to the GUI? For
example: /usr/share/zoneinfo/Asia/Calcutta does not show up in the
GUI. All files available on the Time zone gui tab are in
/usr/share/zoneinfo/zone.tab.
Distribution: RHEL 5.4 (64-bit)

Thanks.