How did the days of the week sync across the world?

Question

Pre-industrial cultures I’m pretty sure had days of the week, but did everyone have a 7-day week?

E.g. in 1290 did Marco Polo leave Italy on a Tuesday, and arrive in China on a Friday (according to him), but the Chinese understood it to be their “Monday” when he arrived.

Do we have any historical sources that give an idea of how/why this happened?

In: Other

Answer 1

The modern Week can trace it’s roots back to the Ancient Romans, who named the days after their gods – those pesky Germanic tribes stole that idea from them, but used their own Gods in place of the Roman gods – that’s how English ended up with the weekday names that it has. Originally Rome actually had an 8 day week (from the Etruscans), but over time it evolved into 7 days. The Romans (specifically Julius Caesar) also developed the modern year calendar, with 12 months totaling 365 days and a leap year once every 4 years (some minor modifications to this happened later). So this is where we get our modern calendar system from.

As Christianity became super important in Europe, keeping track of the particular day of the week became really important because of the emphasis on Sunday in Christianity. Emperor Constantine actually declared Sunday a public holiday. However, the rest of the world continued to use whatever local system had developed there – but in general calendars tended to have something analogous to weeks that lasted somewhere between 6 and 10 days, but this was not a necessary feature of timekeeping systems.

Anyway, back then, the days of the week weren’t as important if you weren’t an official some sort or a religious authority. Most people were illiterate farmers or laborers and just worked as they needed to, and time was kind of loosey goosey. However, eventually two things happened. The first was the spread of European empires across the world – suddenly everyone is being exposed (forcibly) to these Europeans and their calendar that they make a really big deal about. The next thing is industrialization – with the rise of large industries, factories, etc, the economy becomes much more organized around industrial applications – hence there is a larger emphasis on timekeeping for everyone. Since Europe is so economically dominant, everyone else starts using this timekeeping method as either their primary of secondary method.