God made humans on the sixth day of creation (Genesis 1:24-31). God put Adam and Eve in the Garden of Eden and instructed them to dress and keep it, which indicates labor or work (Genesis 2:15). If they obeyed God and went to work the very next day, then they were working on the day God was resting.
Using our Julian calendar in this illustration, God would have begun His creative work on Sunday, made humans on Friday, and then rested on Sunday. If Adam and Even went to work the next day after they were created, then they went to work on Saturday, worked through Thursday, and rested on Friday. Can we prove any of this? Absolutely not.
These two points sound a little difficult, to say the least. Yet if we are to accept as an inviolable decree that we are to cease from physical labor on Saturday, then they need serious consideration.