Ah, I thought that He rested on the yom after the 6th yom. Wouldn't that be the last day of the 7-day cycle? Am I mistaken?
Yes- you are mistaken.
In Jewish custom, “days” start at sunset. It is a sunset to sunrise , not sunrise to sunset.
Understanding the context of the commandments makes a huge difference. That is why we are to learn the ancient ways and seek that ancient understanding. The Sabbath starts at sunset on Friday.
I believe that people can worship either day, but we are commanded to observe the Sabbath, and for a very, very good reason. The placement is important and the context, as always is for a very, very good reason.
The Lord does not just throw things around willy nilly. You can still go to church on Sunday and worship and sing.. (from my understanding) but to observe a Sabbath on the first day of the week is profound.
I hope you will try it and see for yourself, because that is really the only way to understand. :)