On RHEL4+ systems, timezone data files are kept in /usr/share/zoneinfo/ with the /etc/localtime symbolic link pointing at the correct time zone the machine belonging to.
If the time zone data file doesn't contain the correct information, then the system seem to assume its on GMT. Now if the system date and time is set manually to the current localtime, everything appears normal.
One noticed problem that happens in such a setup is if this machine serves as a mail server, then the mail header contains these time zone details. This can cause strange problems with MS Outlook, as outlook seem to use this value and the local machines time-zone details to calculate the display time on mails.
For some reason, the mail clients running on GNU/Linux systems appears to be immune to this problem. Still have find out how the mail clients such as evolution etc. display the received time on mails.
On RHELs the time zone data are provided in tzdata package, and it's important to keep that up2date, specially if it is an online system.
