[tz] RES: Timezone for Brazil

Fabrício Rennó fabricio.renno at sxte.com.br
Tue Oct 10 00:45:48 UTC 2023

Harris, thank you for the reply.

These are the reasons for my suggestion being sent:
- I noticed many samples with "area/country/location" (ex.: America/Argentina/...) and I believe this is a better approach;
- I noticed many Brazilian places listed as time zones, but in fact those are just local times.

As I understand, a time zone is a geographic slice that includes hundreds/thousands of places. So, each country does choose its official time zones and for those time zones they set a special "label" for organizational purpose.

As I've mentioned in my initial e-mail, Brazil officially has 4 time zones (-2, -3, -4, -5), therefore for anything time/schedule related in Brazil a person should opt among only those 4 time zones options.

If a specific region (city, state) chooses to change its time zone reference, this should not affect the time zone itself. Time zone is not local time.

I see that choices were made that generated the current database. Perhaps somewhere on the way of the IANA historical evaluation should have considered the possibility of two branches (official time zones; relevant places local times) or even other detailed lists, instead of just a single list. If it's kept the decision to go only by cities/places this list certainly will take an avoidable large amount of energy over the years (data travelling www, resources awaiting) for nothing so relevant, unfortunately.


Fabrício Rennó
+55 31 98648-8987 (mobile)
+55 31 3643-1014 (office)
www.aico.com.br (conheça)

-----Mensagem original-----
De: Guy Harris <gharris at sonic.net> 
Enviada em: segunda-feira, 9 de outubro de 2023 19:22
Para: Fabrício Rennó <fabricio.renno at sxte.com.br>
Cc: tz at iana.org
Assunto: Re: [tz] Timezone for Brazil

[Geralmente, você não obtém emails de gharris at sonic.net. Saiba por que isso é importante em https://aka.ms/LearnAboutSenderIdentification ]

On Oct 8, 2023, at 9:56 AM, Fabrício Rennó via tz <tz at iana.org> wrote:

>  Brazil has officially 4 time zones.
> Source: http://www.horalegalbrasil.mct.on.br/HoraLegalBrasileira.php
>  Expected listed results:
> - America/Brazil/Noronha(GMT-02:00)
> - America/Brazil/Brasilia(GMT-03:00)
> - America/Brazil/Amazonas(GMT-04:00)
> - America/Brazil/Acre(GMT-05:00)




        Timezones are typically identified by continent or ocean and then by the name of the largest city within the region containing the clocks.

Thus, the IANA database timezones in Brazil, just like time zones in the United States and Canada and Mexico and Germany and India and Nigeria and... do not include the name of the country, and almost always contain the name of a city, not the name of a larger region.

Furthermore, IANA database timezones don't just correspond to regions that all currently share an offset from UTC/GMT; they handle not only the current official offset from UTC/GMT, they also handle rules from switching between standard time and daylight saving/summer/etc. time, and even handle changes to the *official standard time offset from UTC/GMT* (which sometimes *does* happen).

In addition, there may be IANA database timezones that do not correspond to *current* timezones, but that differed from other regions, either in their standard offset from UTC?GMT or in their time-shifting rules, at some point between 1970 and now.

Therefore, the IANA database timezones for Brazil are, with identifications taken from comments in the database source (I'm guessing the two-capital-letter codes are codes for states:

        America/Noronha - Fernando de Noronha (the comments say "administratively part of PE")

        America/Belem - Amapá (AP), east Pará (PA)

        America/Santarem - west Pará

        America/Fortaleza - Maranhão (MA), Piauí (PI), Ceará (CE), Rio Grande do Norte (RN), Paraíba (PB)

        America/Recife - Pernambuco (PE) (except Atlantic islands)

        America/Araguaina - Tocantins (TO)

        America/Maceio - Alagoas (AL), Sergipe (SE)

        America/Bahia - Bahia (BA) (the comments say "There are too many Salvadors elsewhere, so use America/Bahia instead of America/Salvador.")

        America/Sao_Paulo - Goiás (GO), Distrito Federal (DF), Minas Gerais (MG), Espírito Santo (ES), Rio de Janeiro (RJ), São Paulo (SP), Paraná (PR), Santa Catarina (SC), Rio Grande do Sul (RS)

        America/Campo_Grande - Mato Grosso do Sul (MS)

        America/Cuiaba - Mato Grosso (MT)

        America/Porto_Velho - Rondônia (RO)

        America/Boa_Vista - Roraima (RR)

        America/Manaus - east Amazonas (AM): Boca do Acre, Jutaí, Manaus, Floriano Peixoto (the comments say "The great circle line from Tabatinga to Porto Acre divides east from west Amazonas.")

        America/Eirunepe - west Amazonas (AM): Atalaia do Norte, Boca do Maoco, Benjamin Constant, Eirunepé, Envira, Ipixuna

        America/Rio_Branco - Acre (AC)


        1) more than you list;

        2) no "/Brazil" in the names.

Results, on my machine, for 2018-08-04 20:42:19 UTC (chosen because its "seconds since the Epoch" value happened to appear in the "date" manual page on my machine):



        America/Belem, America/Santarem, America/Fortaleza, America/Recife, America/Araguaina, America/Maceio, America/Bahia, America/Sao_Paulo:


        America/Campo_Grande, America/Cuiaba, America/Porto_Velho, America/Boa_Vista, America/Manaus:


        America/Eirunepe, America/Rio_Branco:



        America/Noronha is the only IANA database timezone in the Noronha official Brazilian time zone;

        America/Belem, America/Santarem, America/Fortaleza, America/Recife, America/Araguaina, America/Maceio, America/Bahia, and America/Sao_Paulo are the IANA database timezones in the Brasilia official Brazilian time zone;

        America/Campo_Grande, America/Cuiaba, America/Porto_Velho, America/Boa_Vista, and America/Manaus are the IANA database timezones in the Amazonas official Brazilian time zone;

        America/Eirunepe and America/Rio_Branco are the IANA database timezones in the Acre official Brazilian time zone.

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