The week is the only measurement of time that has its origin in religion. Days, months, and years are determined by the movement of the planets, but God gave us the week.
The Bible says in Genesis that God created the heavens and the earth in six days, and on the seventh day he blessed it and set it aside saying, “Remember the Sabbath (seventh) day to keep it holy (separate and different from the other six days)."
Think of what the week would be like without God. It would be: Sinday, Mournday, Tearsday, Wasteday, Thirstday, Fightday, and Shatterday. Remember the ol' saying that seven days without God makes one weak!