We are in a conversation and discussion about John Walton's (professor at Wheaton) new book, The Lost World of Genesis One: Ancient Cosmology and the Origins Debate.
Proposition 9 is another big one:
The seven days of Genesis 1 relate to the cosmic temple inauguration.
Put this differently: the seven days are not about the duration of bringing matter into existence, but a period of time devoted to inaugurating the various functions of the temple. That is, they prepare the cosmos for God's dwelling and humans as those who are to worship the God in whose temple they dwell.
As with Solomon's temple, the temple was not built until God indwellt it -- so Genesis 1's seven days (Solomon's took seven years) indicates the completion of the temple when God indwells. Genesis 1 could be an enthronement-of-God text used annually.