[tz] Preparing to fork tzdb

[Howard Hinnant]

On Sep 21, 2021, at 1:49 AM, Steve Allen via tz <tz at iana.org> wrote:
> 
> On Mon 2021-09-20T23:34:25-0400 Howard Hinnant via tz hath writ:
>>        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';
> 
>> Output:
>> 
>>    1957-06-06 00:30:10 TAI
> 
> anything that produces a value of TAI for a date in 1957 has created a
> fantasy world that does not correspond to reality.

After I hit send I thought I may have gone a step too far in converting to TAI.  Leaving that conversion out simplifies things and does not negate my point:  that IANA time zone names are part of the C++20 API, and pre-1970 data is expected (best effort of course):

     zoned_time zt{"America/Port-au-Prince", local_days{1957y/June/5} + 19h + 30min};
     cout << format("%F %T %Z", zt.get_sys_time()) << '\n';

Output:

    1957-06-06 00:30:00 UTC

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