Interesting thought which could still be true in spite of the fact that God carved the 7 day cycle in stone with his own finger when He gave Moses the 4th commandment.

For in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day; wherefore the Lord blessed the Sabbath-day and hallowed it. Exod 20: 8-11

"It is a sign between Me and the sons of Israel forever; for in six days the LORD made heaven and earth, but on the seventh day He ceased from labor, and was refreshed." When He had finished speaking with him upon Mount Sinai, He gave Moses the two tablets of the testimony, tablets of stone, written by the finger of God. Exodus 31:18