Many IPhone users woke up one hour earlier in Brazil today
Apparently, the IOS changed the phone time to DST, in last year (2017) the date to start DST in Brazil was october 15 (coincidence, no?).

Maybe this problem already occurred because the first change in DST rule, that changed the start date to november 4, because of the elections dates on Brazil.
If this assumption is correct, we had problems even with 10 months to update the DST rules. 
It's a little sample of what can happen if the DST is changed again with only a few weeks to update all affected devices.

sources:
https://tecnoblog.net/263674/iphone-acertar-relogio-alarme-horario-verao-errado/
https://www.correiobraziliense.com.br/app/noticia/brasil/2018/10/15/interna-brasil,712674/iphone-muda-de-horario-e-usuarios-acordam-uma-hora-mais-cedo.shtml

Em qua, 10 de out de 2018 às 15:39, Stepan Golosunov <stepan@golosunov.pp.ru> escreveu:
11.10.2018 в 00:53:17 +0800 Phake Nick написал(а):
> In fact railroad in countries like Kazakhstan, Russia, China do follow time
> of their capital and thus you need to use Moscow time even if you're taking
> a train at Vladivostok, which it doesn't appears to be convenient.

That's no longer true for Russia:
http://eng.rzd.ru/newse/public/en?STRUCTURE_ID=15&layer_id=4839&id=107332

> 在 2018年10月10日週三 02:44,Paul Eggert <eggert@cs.ucla.edu> 寫道:
>
> > Lester Caine wrote:
> > > That IATA is now complaining about the very short notice
> >
> > If *I* were running an airline, I'd issue tickets with times in UTC only.
> > That
> > would solve *that* problem.
> >
> > And perhaps that's why I'm not running any airlines....
> >