timezone

Sources for Time Zone and Daylight Saving Time Data
http://www.twinsun.com/tz/tz-link.htm

Olson database of timezones in posix.1 format
http://fixunix.com/ntp/68031-olson-database-timezones-posix-1-format.html

Zoneinfo contains historic and future timezone information and is not
limited to two offset values each year, or to algorithmic rules for
deciding when to change, which is why you can only substitute Posix format
code over limited time periods where those assumptions are valid.

If you want to enumerate all the possible timezone codes used by the
Olsen package, you should look at the source code for the rules.
Even if you don't have the source of the tables (which is free to download),
you can use zdump to enumerate all the changes for a particular file.

POSIX and Olson time zone formats
http://www.ibm.com/developerworks/aix/library/au-aix-posix/index.html?ca=dat
AIX Health Check - Olson time zone support
http://www.aixhealthcheck.com/blog?id=291

One of the biggest advantages is that Olson database maintains a historical record of what the time zone rules were at given points in time, so that if the rules change in a particular location, dates and times can be interpreted correctly both in the present and past. A good example of this is the US state of Indiana, which just began using daylight saving time in the year 2006. Under the POSIX implementation, Indiana would have to set its time zone value to EST5EDT, which would format current dates correctly using daylight saving time, but would also format times from previous years as though they were on daylight saving time, which is incorrect. Use of the ICU API set for time zones also allows for localized display names for time zones. For example, Central Daylight Saving Time would have an abbreviation of CDT for all locales under a POSIX implementation, but under ICU/Olson, it displays properly as HAC (Heure Avancée du Centre) in a French locale.

tz database - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Tz_database

time - organization of zoneinfo folder - Ask Ubuntu
http://askubuntu.com/questions/34925/organization-of-zoneinfo-folder

If you install the tzdata source package, you will find all your answers:

sudo apt-get install apt-src
mkdir tzdata && cd tzdata
apt-src install tzdata

Specifically:
posix and right:

Two different versions are provided: - The "posix" version is based on the Coordinated Universal Time (UTC). - The "right" version is based on the International Atomic Time (TAI), and it includes the leap seconds.

Etc:

These entries are mostly present for historical reasons, so that people in areas not otherwise covered by the tz files could "zic -l" to a time zone that was right for their area. These days, the tz files cover almost all the inhabited world, and the only practical need now for the entries that are not on UTC are for ships at sea that cannot use POSIX TZ settings.

EST5EDT, ...:
GB, GB-Eire, GMT, GMT+0, GMT-0, GMT0, NZ, NZ-CHAT, PRC, ROC, ROK, UCT, UTC are there because the time zone names changed:

This file provides links between current names for time zones and their old names. Many names changed in late 1993.

CET, CST6CDT, EET, EST, EST5EDT, HST, MET, MST, MST7MDT, PST8PDT, WET are there for backwards compatibility.

From Arthur David Olson, 2005-12-19 We generate the files specified below to guard against old files with obsolete information being left in the time zone binary directory. We limit the list to names that have appeared in previous versions of this time zone package. We do these as separate Zones rather than as Links to avoid problems if a particular place changes whether it observes DST. We put these specifications here in the northamerica file both to increase the chances that they'll actually get compiled and to avoid the need to duplicate the US rules in another file.

dpkg - How do I change my timezone to UTC/GMT? - Ask Ubuntu
http://askubuntu.com/questions/138423/how-do-i-change-my-timezone-to-utc-gmt

$ date
Wed Jul 16 22:52:47 EDT 2014

$ cat /etc/timezone
America/New_York

$ sudo dpkg-reconfigure tzdata
$ service cron stop && service cron start

How to change timezone on Linux server? | Linux cPanel WebHosting Blog
http://www.theperfectarts.com/2009/11/how-to-change-timezone-on-linux-server/

root@admin[~]#date
Wed Nov 11 19:30:29 EST 2009
For example we are changing time zone  from EST to GMT.
root@admin[~]#ln -sf /usr/share/zoneinfo/GMT /etc/localtime

UbuntuTime - Changing the Time Zone
https://help.ubuntu.com/community/UbuntuTime

linux - Does NTP daemon set the host timezone? - Server Fault
http://serverfault.com/questions/194402/does-ntp-daemon-set-the-host-timezone

NTP does not handle time zones. All time data handled by NTP is in UTC; your local time zone setting determines the offset from there.

How time zones are handled with NTP?
http://www.meinbergglobal.com/english/faq/faq_32.htm

NTP does not regconize time zones, instead it manages all time informations based on UTC. In general the handling of time zones is a job of a computer's operating system. Under Windows, Linux and FreeBSD the system clock is based on UTC, the configured local time zone only is applied when a time information has to be displayed somewhere. Example: If you configure Windows to use your local time zone, the system clock continues with using UTC time. Only when the date/time is shown (e.g. in a clock application), it will be transformed from UTC into the locally configured timezone.