Dietrich Bonhoeffer, clarifying why debates over “day” in Genesis are exercises in missing the point:

When the Bible speaks of six days of creation, the term “day” may well have been meant in the sense of a day of morning and evening. Even so, however, it did not mean such days as periods of time that one could just count up; instead what is being thought of is the power of the day, which alone makes the physical day what it is: the natural dialectic of creation. Where the Bible speaks of the “day,” it is not at all the physical problem that it is discussing. Whether the creation occurred in rhythms of millions of years or in single days, this does no damage to biblical thinking. We have no reason to assert the latter or to doubt the former; the question as such does not concern us. That the biblical author, to the extent that the author’s word is a human word, was bound by the author’s own time, knowledge, and limits is as little disputed as the fact that through this word God, and God alone, tells us about God’s creation. God’s daily works are the rhythms in which the creation rests.