In /etc the file, localtime, is a link to or copy of a file containing information about your time zone. Zone information files are usually in /usr/share/zoneinfo but this depends on your distribution. So if your localtime file points to a zone info file that is not your time zone you can change it by browsing the directories in /usr/share/zoneinfo to find your country, then find your city or a city in the same time zone and link localtime to it.
|# ln -sf /usr/share/zoneinfo/Asia/Jakarta /etc/localtime|
Some applications may use the configuration file /etc/sysconfig/clock to determine the current time zone so it's a good idea to set the ZONE entry (e.g. "Asia/Jakarta").