[tz] TZDB Questions

Guy Harris guy at alum.mit.edu
Tue Aug 28 06:33:00 UTC 2018

On Aug 27, 2018, at 8:46 PM, Paul Eggert <eggert at cs.ucla.edu> wrote:

>   1. Has there been any consideration to move the source data into a more
>   structured format like csv, xml, or json?

Source code and data is something to be edited and read by humans, so a less-structured but more readable format, as long as it *can* be parsed by software, is preferable.

>   I realize I'm probably in the
>   minority here in terms of people who would find this useful.

There's "make the source file CSV/XML/JSON files" and there's "make CSV/XML/JSON files containing the time zone data available"; the latter can be done without doing the former, just as "make binary files containing the time zone data available" was done without the former when the project began - a program like zic, or zic itself, could read the source files and emit CSV/XML/JSON files, once an appropriate schema is devised.  I suspect the latter would be as useful as the former.

>   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   this method where they point to an outdated rule set whereas most non-dst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 = '-')?

Do any tzdb regions that used to observe DST but no longer do so implement that by adding an additional zone line, with no rule set, rather than by having the last zone line point to a rule set where the last rule ends when DST observation didn't end?

>   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
>   oversight.)

We may need to clarify that the first of these two items in the theory.html file takes precedence over the second, unless the use of "should" rather than "must" in the second is sufficient:

	• Uninhabited regions like the North Pole and Bouvet Island do not need locations, since local time is not defined there.
	• There should typically be at least one name for each ISO 3166-1 officially assigned two-letter code for an inhabited country or territory.

>   5. Do you have a favorite time zone? I've become quite fond of
>   Antarctica/Troll both for its name and its unique offset.

US/Pacific-New, until we stopped waiting for it to happen and just linked it to America/Los_Angeles. :-)

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