Mentioning previous answers is intended as a starting point, not to discourage follow-on questions, info, or debate.

There's an FAQ section at https://www.reddit.com/r/AskHistorians/wiki/calendars#wiki_weeks.2C_weekdays.2C_and_weekends

In the app, the "#" anchor doesn't work, so on that "Calendars and timekeeping" page, it's section Weeks, weekdays, and weekends

There are three discussions that look most pertinent to your question:

• "Was there ever a point in history where in some part of the world (a significant settlement) a week was not 7 days? How come we have 7 days to a week all over the world now?" at https://www.reddit.com/r/AskHistorians/comments/uvsog/was_there_ever_a_point_in_history_where_in_some/ , /u/Duck_of_Orleans , /u/Algernon_Asimov
• "What were different cultures' and different time periods' equivalent of the Judeo-Christian seven day work week?" at https://www.reddit.com/r/AskHistorians/comments/v42xc/what_were_different_cultures_and_different_time/ . Algernon_Asimov again, /u/iwsfutcmd
• "When did the week become standarized across the world? Has there ever been differences in the day of the week, e.g. Tuesday in Germany but Friday in Russia?" at https://www.reddit.com/r/AskHistorians/comments/1w76k0/when_did_the_week_become_standarized_across_the/ , with much about the "weekend" concept. Algernon_Asimov again.