Adam and Eve had no conception of the Sabbath - they never worked or labored for anything prior to leaving the garden. God walked and talked with them daily, whenever apparently - what need for their to be to recognize that which is accessible and available all the days.

What purpose would a God have at all for the life inside his creations to set aside 1/7 of their time "for him" anyways?

Lots of silly, silly stuff people say God thinks