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My questions are related to /usr/share/zoneinfo folder.

  • Why is there a posix folder, which has the same content and files like zoneinfo? I only checked few files and they had same checksum.
  • Why is there a right folder? As far as I know are in there timezone files which contains time with no leap years, because every year has all the seconds. No one uses this anymore.
  • Why is there a Etc directory? In there are GMT+/-number files which, so I heard, doesn't have daylight saving time.
  • Why is there a lot of time zone files like this EST5EDT, PST8PDT, CST6CDT, ROK, ROC, etc? That doesn't make any sense to me.

Any other information about this folder and files or general information about timezone files would be much appreciated.

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1 Answer 1

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.

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