[tz] Fwd: TZDB Questions

Paul Eggert eggert at cs.ucla.edu
Tue Aug 28 03:46:38 UTC 2018

[Forwarded with permission.]

-------- Forwarded Message --------
Subject: TZDB Questions
Date: Mon, 27 Aug 2018 17:52:53 -0700
From: Mikey Schott <maschott at gmail.com>
To: eggert at cs.ucla.edu

Hello, Dr. Eggert. First let me express my thanks to you for all of the
time and energy you have put into the upkeep of the time zone database. I
appreciate all of the thought and detail that goes into the decisions
regarding each zone.

I've been working extensively with the time zone database over the past
month to identify a list of currently unique time zones for use in a
front-end web application. I'd be happy to share the details of my work if
you are curious, but since its purpose is tangential to that of the time
zone database, I'll leave them out of this email.

The reason I'm writing is because after working so closely with the data, I
had a few questions I was hoping you could answer for me. I have more or
less completed the work I was doing, so these questions come more from
curiosity than necessity.

    1. Has there been any consideration to move the source data into a more
    structured format like csv, xml, or json? I realize I'm probably in the
    minority here in terms of people who would find this useful.
    2. The latest zone entry for some zones that no longer use dst still
    point to dst rules, e.g. Asia/Tokyo and the Japan rule set even though dst
    is no longer used in Japan . Is there a reason why some non-dst zones use
    this method where they point to an outdated rule set whereas most non-dst
    zones use no rule set (i.e. rule = '-')?
    3. I've noticed that some zones just use a shortened version of their
    offset for their format, whereas timeanddate.com gives them a more
    descriptive format (e.g. Europe/Volgograd uses MSK vs. +03). Is there a
    reason for the discrepancy? Does the time zone database error on the side
    of caution here?
    4. I believe that one of the primary purposes of the Link zones is to
    ensure that there is a zone that covers every country. Is there a specific
    list or source that the time zone database uses to decide the list of
    countries that are covered? I noticed that Bouvet Island (BV) and Heard and
    McDonald Islands (HM) are not included despite having ISO-3166-2 country
    codes. (Although both have a population of 0, so it hardly qualifies as an
    5. Do you have a favorite time zone? I've become quite fond of
    Antarctica/Troll both for its name and its unique offset.

Thanks again for all of your work on the database. I've signed up for the
mailing list so I can keep up to date.


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