[ELI5] When and how did the days of the week sync up globally?

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I think people have had weeks with assigned days for thousands of years, but with travel taking as long as it does I’m sure there have been many times in history where different cultures were ‘on different days’ at the same time.

I wonder when did it come to be that Monday is the same day in China as it is in Chad? Was it forced upon the conquered in, say, Roman times? Or was it one of those more modern standatizations?

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4 Answers

Anonymous 0 Comments

It’s semi-modern; and the result of Christian/Muslim colonization.

While almost every culture divides time into years (one cycle of the seasons) and months (one cycle of the moon); the modern week is a Jewish thing that carried into Christianity and Islam, based on God’s decree that one day in seven be set aside for rest. Before converting to Christianity, Rome had an 8-day week; and other cultures had as few as 4 or as many as 10 days in their week.

Anonymous 0 Comments

What you’re talking about is basically the slow standardization of the planet on the Gregorian calendar. That was an upgrade of the Julian calendar, which was a Roman thing.

There’s lots of obvious value in everyone being synchronized, particularly as long-distance travel became easier. There’s nothing magic about the Gregorian calendar, but it had a head start in the Western world thanks to the Roman empire, so it became the basis for most of Europe, then followed all the European powers on their colonization binge. At that point it had covered most of the planet so when we all converged on one that was an obvious candidate.

It didn’t happen all at once, it’s still not done. There are lots of places that still maintain multiple calendars.

Anonymous 0 Comments

Maybe there might have been confusion early on? But in reality, it’s not hard to figure out that we had to designate an “International Date Line” and add or subtract a day whenever we travel across it.

Anonymous 0 Comments

Because countries thought it was in their best interest to adopt the Gregorian Calendar. Once they decided to switch, they had to figure out the one-to-one match from their old calendar to the Gregorian calendar, and then declare a date when the new system was in effect. So in effect they said “the day of the week we call x, d/m/y becomes Monday new-d/new-m/new-y on this date.”

Why did it happen? It was a slow process where countries using their own calendars found the confusion in communicating with other countries greater than the confusion caused by switching.

The Pope created Gregorian calendar in 1582. UK switched in 1752, Russia in 1918. Other countries switched or started using Gregorian when their Western European influence increased. Saudi Arabia was last in 2016. Before that it was Greece in 1923.