I received my confirmation instruction from a Pastor who was faithful to teach from the Luther's Small Catechism. And all my life I have worshiped in Lutheran congregations where we recite the creed (Apostles or Nicene) every Sunday. Nowhere do any of these speak of a doctrine of six day creation. I would guess that the church has generally seen a belief in God's creation, of all that is, the primary truth of the Bible. And that a six day creation is not central to the advancement of God's kingdom.