The Brazilian Government has just issued a law that shifts the beginning of the Brazilian DST (Daylight Saving Time) locally called as Summer Time.

This new DST date will come into force in the next month, to be more precise on 18th of November of 2018. So, we won't have enough time to wait for a new Olson update through the operation system updates, neither downloading a new Olson database package might be enough.

I have downloaded the file tzdb-2018e.tar.tz from https://www.iana.org/time-zones. Inside that package I found the file southamerica and I have located the following entry:

# From Steffen Thorsen (2017-12-18):
# According to many media sources, next year's DST start in Brazil will move to
# the first Sunday of November, and it will stay like that for the years after.
# ... https://www.timeanddate.com/news/time/brazil-delays-dst-2018.html
# From Steffen Thorsen (2017-12-20):
# http://www.planalto.gov.br/ccivil_03/_ato2015-2018/2017/decreto/D9242.htm
Rule    Brazil  2018    max -   Nov Sun>=1  0:00    1:00    -
Rule    Brazil  2023    only    -   Feb Sun>=22 0:00    0   -

The comments preceding the entry rule for 2018 matches the old law from the end of 2017, but there's a new law that shifts it to the 3rd Sunday of November of 2018.

How to fix that Olson entry shifting it to the 3rd Sunday of November? I have tried Sun>=3 yet, and it didn't work.

  • That's really short notice - please lobby your appropriate representative(s) so they know why such changes are problematic. If it's any consolation, it's probably harder for those stuck on proprietary OSes to update their own zone DBs. – Toby Speight Oct 9 '18 at 16:06
  • @TobySpeight: I've been thoughting about that. And that is why I ask myself, why do Data Centers and big IT companies don't yell at the representatives (or at news to form public opinion)? I've no clue. (although I think that the president has the power to do this mess without the representatives polling) – Luciano Oct 9 '18 at 17:52
  • Was not the target that already changed several times? – Rui F Ribeiro Oct 10 '18 at 12:58

You need to specify Sun>=15: the third Sunday is the first Sunday which is also the fifteenth or greater day of the month.

These kind of last-minute changes have been successfully dealt with in the past through distribution updates; there’s a decent chance there will be an update soon. (This doesn’t help people who need to deal with dates in November right now, of course.)


You can get it from github actually, it has been modified 5 days ago.

see https://github.com/eggert/tz/blob/master/southamerica for the southamerica tz file

and https://github.com/eggert/tz/commit/efda0562d7fc7bc90b6cab76998fab8b4953e056 for the relevant commit

Southern Brazil starts DST two weeks later in 2018 * NEWS: Mention this. * southamerica (Brazil): New rule just for spring 2018.

eggert committed 5 days ago

 - Rule Brazil  2018    max -   Nov Sun>=1  0:00    1:00    -
 + # From Fábio Gomes (2018-10-04):
 + # The Brazilian president just announced a new change on this year DST.
 + # It was scheduled to start on November 4th and it was changed to November 18th.
 + # From Paul Eggert (2018-10-04):
 + # This attempts to avoid confusion during the November 4 and 11 national high
 + # school exams, which were mis-scheduled.  Guess that it's just this year.
 + Rule Brazil  2018    only   -    Nov Sun>=15 0:00    1:00    -
 + Rule Brazil  2019    max    -    Nov Sun>=1  0:00    1:00    -

As for publishing the new update in the official TZ tables - aka 2018f:

[tz] Another change on Brazilian DST time

Paul Eggert eggert at cs.ucla.edu Thu Oct 4 15:37:17 UTC 2018

I just now updated the development version https://github.com/eggert/tz with the attached patch, and you can use that now if you like. I'd like to plan for a new tzdb release soon after the presidential decree is published (please let me know when that happens).

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.