[tz] question re zone America/Punta_Arenas in Chile

Paul Eggert eggert at cs.ucla.edu
Fri Jul 1 18:12:37 UTC 2022


On 3/18/22 09:09, Michael H Deckers wrote:
>
>    On 2022-03-16 03:24, Tim Parenti via tz wrote:
>>
>> https://www.diariooficial.interior.gob.cl/publicaciones/2018/11/23/42212/01/1498738.pdf 
>>
>
>
>    • Law Number 8,522 was promulgated on 1946-08-28, not the day before.


Although the above URL indeed reprints the 1946-08-28 publication in 
Diario Oficial, I don't see a promulgation date there. 
<https://www.bcn.cl/leychile/navegar?i=285254> says law 8,522 was 
promulgated the day before. That being said, the law says it takes 
effect when it's published so the promulgation date doesn't matter to us.


>
>    • That law contains an "artícolo transitorio" which specifies:
>
>            Artícolo transitorio. Al tiempo de entrar en vigor la presente
>            ley, se fijará la hora oficial para toda la República con
>            arreglo al horário de Verano señalado en el artículo 1.o.
>
>            (Transitional article. At the time when this law takes effect,
>            the official time for the whole Republic will be set according
>            to summer time as indicated in the 1st article.) [my 
> translation]
>
>      That article would be superfluous if the switch to summer time had
>      happened on 1946-09-01 (as tzdb currently says) because that
>      would have been the switching date already indicated in article 1.
>      Thus, the switch to summer time happened earlier than 1946-09-01
>      (as wrongly stated by Shanks).

Yes, and we already have Santiago switching to -03 daylight saving time 
(I wouldn't call it "summer time" :-) on 1946-07-15.


>
>    Hence, both tzdb timezones should be amended:
>
>        Zone America/Santiago  ...
>       -     -4:00   1:00    -03     1946 Sep  1 # central Chile
>       -     -4:00   -       -04     1947 Apr  1
>       +     -4:00   1:00    -03     1946 Aug 29 # central Chile
>       +     -5:00   1:00    -04     1947 Apr  1
>
>        Zone America/Punta_Arenas ...
>       -     -4:00   -       -04     1947 Apr  1
>       +     -4:00   -       -04     1946 Aug 29
>       +     -5:00   1:00    -04     1947 Apr  1
>
>    It would take further evidence (such as newspaper clips) in
>    order to ascertain the precise hour of the switch in both
>    cases.

It would indeed be good to have further evidence. Strictly interpreted, 
the Chilean law published August 28, 1946 required citizens in Punta 
Arenas to move their clocks back an hour immediately, and then forward 
an hour on August 31. I very much doubt whether that's what was intended 
or what citizens did; surely they just kept their clocks on -04. 
Although the TZDB change you're proposing does that, it sets tm_isdst on 
August 29 even though neither the law nor the previous practice said DST 
was being observed August 29. I expect it's better to set the DST flag 
when the new law said DST started. (I doubt whether newspapers will help 
us resolve the tm_isdst issue, as there would be no practical reasons to 
tell the citizens to do anything to their clocks.)

Similarly, the law required citizens in Santiago to move their clocks 
back *two* hours on August 28 (from -03 to -05), and then forward an 
hour on August 31. This is also implausible. Surely they just picked a 
time to move back an hour from -03 to -04. Here, I think it more likely 
that it was done at the end of August 31, since that would have given 
more time to notify the citizens of the change.

I was just talking to my father about this, and he jokingly suggested 
that I fly down to Santiago and check printed newspaper archives there. 
Unfortunately that would take more time than I can spare....

Proposed patch attached and installed into the development database.
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