Earlier quoted context omitted.
Any choice is arbitrary. What is a week to the solar system? The only things that are real are days and years.
What is a day in the solar system? What is anything anywhere anyway? That’s not the point. The point is that in the US people typically work Mon-Fri and loaf around Sat-Sun (weekend) and yet the week starts in Sundays. It’s infuriating.
So now when we rest, both the Jews and the Christians get their favorite day off and yay, we have a two-day weekend.