That's just Eurocentric imperialism pushed onto the world.
But in saying that, a week is just a construct. It's not really a measure of time.
1 day is basically a revolution of the earth on its axis.
1 month is roughly a completion of the cycles of the moon (one month revolution around the earth). But days have been added in most months so it doesn't track anymore.
One year is the plus/minus one rotation of the earth around the Sun. Leep year structure sorts out most of the variance.
But what is a week. It's not based on anything that I know. So who cares when it starts or ends as it's cyclical. If the end is a Saturday or a Sunday or a Wednesday it makes no difference.
Also the Ritalin has kicked in.