I wrote "mostly ultimately because of", so I did mean to say that I thought the Biblical narrative was the historical reason that most cultures and languages that use this numbering did so.
I'm pretty curious about this question, which I've previously asked in the form of "for how long has there been a worldwide consensus about which day of the week it is?". One answer that I heard is sort of akin to sudosysgen's account, in that some people suggested that the question might not be meaningful: there may have been different cultures with a seven-day week and, when they made sustained contact, instead of debating with each other about "which day of the week it is", they may have understood themselves to be translating their existing names for the weekdays -- some of which were based on numbers.
To the extent that that's a good way of talking about it, I also don't have a good understanding of when those translations would have happened, or who would have made them.
It most likely comes from Greek, as the first time the Bible would be translated in a language where days had names. Some Greek calendars used the seven day week which seems to originate from the Sumerians, and naturally the day of the Sun would be the choice for the first day in the Greek pantheon.
I just looked in the Septuagint and (I guess unsurprisingly) it uses ἡμέρα μία, ἡμέρα δευτέρα, ἡμέρα τρίτη. So it wasn't literally directly in the translation process. One could also say that the Genesis text is counting days rather than naming them, as Genesis 1:5 for says יוֹם אֶחָד ('one day') whereas the "name" of the day in Hebrew is יוֹם רִאשׁוֹן ('first day').
This author argues that the "the Jewish, biblical week and the planetary week of astrological origin" were combined in Rome rather than Greece, while agreeing that there are earlier antecedents for the use of the seven-day week.
Wikipedia on "nundinae" seems to roughly agree with this interpretation:
> The 7-day week first came into use in Italy during the early imperial period. For a time, both systems were used together, but the nundinae are seldom mentioned in extant sources after the Julio-Claudian period. The nundinal cycle had probably fallen out of use by the time Constantine adopted the Hebrew weeks for official use in AD 321, altering the day of rest by declaring the Lord's day the Day of the Sun (dies Solis) a legal holiday. Different scholars have placed the end of 8-day markets at various dates from the late 1st to early 5th centuries.
I'm pretty curious about this question, which I've previously asked in the form of "for how long has there been a worldwide consensus about which day of the week it is?". One answer that I heard is sort of akin to sudosysgen's account, in that some people suggested that the question might not be meaningful: there may have been different cultures with a seven-day week and, when they made sustained contact, instead of debating with each other about "which day of the week it is", they may have understood themselves to be translating their existing names for the weekdays -- some of which were based on numbers.
To the extent that that's a good way of talking about it, I also don't have a good understanding of when those translations would have happened, or who would have made them.