I think this excerpt from one of the sites I visited bears repeating.

One day of rest in eight makes the week seem too long. One day in six or five makes the week seem too short. But a day of rest in seven has worked out just right for civilizations down through the centuries.

Where did the seven-day week come from?

It came from God. In the book of Genesis in the Bible we read that God created the world in six days and rested on the seventh. In the book of Exodus (chapter 20) we find that God made this pattern for humans to follow. He even put it into the Ten Commandments He gave to Moses.

The seven-day week has worked remarkably well in every century and in every country because God gave it to us. Those who don't accept this explanation are left with no convincing explanation for its origin. God created us, so He knows what is best for us. That's why we have a seven-day week.

So now you know.

Murray