[tz] Preparing to fork tzdb

[Howard Hinnant]

On Sep 21, 2021, at 11:15 AM, Jan Engelhardt <jengelh at inai.de> wrote:
> 
> 
> On Tuesday 2021-09-21 16:45, Howard Hinnant wrote:
>>>>>>      zoned_time zt{"America/Port-au-Prince", local_days{1957y/June/5} + 19h + 30min};
>>>>>>      cout << format("%F %T %Z", clock_cast<tai_clock>(zt.get_sys_time())) << '\n';
>>>> 
>>>> [...] IANA time zone names are part of the C++20 API, and pre-1970 data
>>>> is expected (best effort of course)
>>> 
>>> I can't really find substance to this claim.
>>> The API [speaking of the locate_zone() function] wants a string, but it does
>>> not specify which particular string value(s)
>> 
>> In the end we believed that this sentence was the best way to
>> describe the set of time zone names:
>> 
>> http://eel.is/c++draft/time.zone#general-1
>> 
>>> [time.zone] describes an interface for accessing the IANA Time Zone Database
>>> [...]
> 
> 
> With a standard wording so loose, the best interpretation I can give you is that
> the minimum set of known names in C++20 is that of tzdata1996l.

Here are detailed instructions for making suggestions to improve the wording of the C++ standard.  Everyone is welcome to contribute: https://cplusplus.github.io/LWG/lwg-active.html#submit_issue

> 
> Which may be lacking America/Port-au-Prince. (Probably not, but humour me.)

The C++20 spec also has API to inspect the version of the time zone database.

Howard

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