You should understand that any Unix computer understands time fundamentally as UTC time. The internal format of timestamps is always UTC-based. Whenever a local time is needed, the OS will convert the UTC-based internal format to the local time of the desired timezone.
When making time changes, first ensure that the system's understanding of the UTC time is correct: type "date -u" and verify that it displays the correct UTC time.
If UTC time is correct but local time is wrong, you have a timezone problem. Trying to fix it by changing the system time will cause other problems (e.g. you cannot use NTP time synchronization if your system's concept of UTC time is skewed to correct localtime errors, because NTP will always force the UTC time to correct value).
IF you want just to stop using the Daylight Saving Time rules, edit /etc/TIMEZONE and remove the Daylight Time part of the timezone specification.
For example, if you live in WST-3WSTDST and want to stop observing DST, change the timezone definition to just "WST-3". There is no need to change the rules in /usr/lib/tztab for this: the number "-3" in the timezone definition lets the system know the correct UTC offset, and the letters "WST" are just a human-readable name.
If you wish to start using a _new_ Daylight Saving Time scheme, you need to edit /usr/lib/tztab.
After changing /etc/TIMEZONE, you must logout & login (or change the TZ environment variable in your session) to make the change effective for your session. You must also restart all long-running processes (crond, syslogd, inetd and all server applications) to make them aware of the new timezone.
(The normal environment variable inheritance rules: login sessions read /etc/TIMEZONE when executing /etc/profile, and all the other processes get a copy of ther parent process's environment at the time they're started.)
The best way to make sure all processes are aware of the new setting is to reboot the system.
MK
