Earlier quoted context omitted.
> Per my knowledge US is the only country which stubbornly (and illogically) considers Sunday to be the first day of the week /Officially/ almost everyone has standardized on ISO 8601 where Monday = 1 and Sunday = 7. But unofficially, not really. The week is still popularly understood to start on Sunday in English Canada, and probably some other parts of the English-speaking world. A quick check of Wikipedia suggests…
> A quick check of Wikipedia suggests Arabic, Portuguese and Vietnamese, all use number-based systems to name the days of the week, and they are indexed from Sunday = 1. But yes, the other is more common. Most of the Slavic languages, and Chinese, among others, use indexed from Monday = 1. For portuguese the name being number based has nothing to do with when the week starts, portugal is historically a very christian…
Now, since Jesus and his resurrection are much more important in Christianity than the creation of the world, the Sabbath began losing its importance, and so renumbering the week started making sense, but was a contentious religious and political issue for a long time. Of course, having two rest days, and one of them being based on Jewish customs in a quite anti-semitic medieval Europe, played a part as well in wanting to change things.
I'm relatively sure that the Portuguese week day names are based on the original Jewish week.