God created the heavens and earth in six days and rested on the seventh. The Sabbath Day is the seventh day, connected to when God rested. The 8th day or Sunday, would begins a new cycle of creation; new work week. Let there by light would have occurred on the first Sunday; day 1, so seven days add up to Saturday.
The question becomes how long did God rest, since a heavenly day is not necessarily the same as an earth day? Also, by the rules of the Sabbath, one is not supposed to work on the Sabbath. Who was working for God as God rested to recharge his batteries?
Like the human Sabbath, God would have made provisions for others to do the tasks that need to be done; feed the animals, as he rested. Such provisions were set up in Eden; tree of knowledge of good and evil and Satan appear. God warns Adam and Eve, but he does not stop them, because he was resting on the Sabbath. Adam and Eve end up in another place to be cared for, as God rested in paradise. They came to the earth ruled by Satan and law; Lord of the Earth.
When did/does the Sabbath rest of God end? There is no clear cut quote for this. However, this might be inferred by looking for God caliber creation appearing once again. The litmus test would need to be beyond what science can explain. This happens near the end of Revelations after the Rapture; Heavenly Jerusalem descends to the earth made of precious materials. There is nothing as spectacular as that, in the Bible, after the first six days of creation, until that time. This seems to suggest that God has gone back to work; day 8 or the second Sunday.
What is interesting is the Jews see Saturday as the Sabbath; day of rest as God rested, while the Christians see Sunday as their day of rest. This would mean the Christians; Gentiles, had to work on the Saturday Sabbath as God rested; supported the Jewish Sabbath. They got their day of rest; Sunday, when God comes back online, and starts his second work week. Wipes away all their tears.
In the end of Revelations, God creates a new heaven and earth. He is fully back online and decides to start from scratch and do it right the second time, without Satan. There is no more law, with the Tree of Life appearing again with its twelve type of fruits and leaves for healing the nations; software and firmware updated.