Exactly Tracy. The seven days of creation are Old Testament, therefore Jewish. They go to synagogue on Friday evening then celebrate the Shabbat (sabbath as we would say) in compliance with that. What we now call Sunday was the first day of their working week as it was too throughout the ancient Persian Empire, the Babylonians and the Germanic/Nordic countries. The Germanic Name became our Sunday, the day of the sun, then by their understanding the distance of each celestial body, Monday (moon), Tuesday (Tir or Tyr, Mars as in Mardi), Wednesday (Wotan or Odin, Mercury as in Mercredi), Thursday (Thor, Jovis in Latin hence Jeudi, Jupiter), Friday (Freya, Latin Veneris as Vendredi, Venus) and Saturday (Saturn). OK, the Norse people got the calculation of Venus wrong and put Friday in the wrong place! Uranus, Neptune and Pluto were not known, thank providence or our week may been very long. Also using the mnemonics My Very Elegant Mother Just Served Us Nine Pies, My Very Easy Method Just Speeds Up Naming Planets, Mercury's Volcanoes Erupt Mulberry Jam Sandwiches – Umbrellas Needed! or My Very Educated Mother Just Saved Us Nine Pence(Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto) you have the correct order. The Babylonians gave us astronomy as we still have it, if a bit further on. Anyway, the point is that the Sun always comes first, because in any creation theory that is relevant the sun rose on the first day and life began.
No Tracy, I don't know all of that but have a little book from our almost annual school visit to the Royal Greenwich Observatory whose director was an old boy of the school in those days. So I cribbed it from that. That is where it tells me that astronomically each cycle, or calendar week, in the western world begins on Sunday. France is different because after the 1792 purges of clergy and temporary suspension of religious celebration they 'abolished' Sunday but to drive the point home made Monday the first day of the week. A few countries have adopted that, but not many, so strictly speaking the week begins, not ends, on Sunday. As for the 'working week' which starts on Monday, that is a throwback to when bookkeeping was not carried out on Sundays, therefore people were paid from Monday to Saturday, the day of rest was actually the beginning of the week to rest them to prepare them for work. Oh such fun playing with trivia to prove that weekend is oxymoronic.