[tz] Request for change to the tz database

Guy Harris gharris at sonic.net
Tue Feb 9 03:35:01 UTC 2021

On Feb 8, 2021, at 4:39 PM, John Hawkinson <jhawk at alum.mit.edu> wrote:

> 2) As I raised earlier today, the validity of a tz identifer is about more than just the user interface for timezone selection, which is essentially a "solved problem," even if not every software package has solved it. That UI doesn't do anything for the people who ask, "What zone is my computer set to?"

What sort of answer are they expecting?  "Pacific time zone"/"Pacific time"?  "US Pacific time zone"/"US Pacific time"?  "The zone for {one of San Francisco, San Jose, Los Angeles, Menlo Park, ... (depending on what level of town/city is offered by the TZDB region selecting UI}"? Or "America/Los_Angeles"?

The answer may depend on which such person you ask.  Most people probably aren't familiar with the fine details of changes in DST rules - or even changes in *time zone* in the sense of "standard time offset from UTC" - in the history of a particular TZDB region, so a TZDB ID may be irrelevant to them, and it would probably be meaningless as well.

Those who *do* understand TZDB regions (as opposed to "time zones") and want to know the TZDB region ID for the system should, if they're not already aware that the region IDs:

	don't necessarily correspond to the city nearest you, don't necessarily correspond to the *large* city nearest you, and don't necessarily correspond to the "most important" (by some criterion) city in the region;

	use "America" to refer to the Americas, not to the United States of America;

	don't necessarily arrange that the city used for the region you're in is closer to you than the city used for some *other* region;

	may not use the preferred English-language transliteration of the city's name;

should be made aware of that.

I.e., there are non-technical users, who should never have to see a TZDB ID unless they're reporting it to a support person, and technical users, who *do* need to know TZDB IDs, and the latter should understand the above characteristics about TZDB IDs.

> or those who ask, such as through the Google Timezone API https://developers.google.com/maps/documentation/timezone/overview, "What is the TZ identifier for this location or for this long/lat pair?"

Only technical users should do that directly.  Non-technical users users should be running software that does that for them and Does The Right Thing without showing them a TZDB ID.

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