The B.B. could be explained in Genesis 1:1- In the beginning God created the heavens and the earth. So everything is possible with God.
I am hearing from some Christian theologians that I respect their views well, that they believe in a pre-Adamic earth (a gap theory) between Gen.1:1 and 1:2.
So, the B.B. theory has the billions of yrs. Ago timeline -which is possible for Genesis 1:1.
So, maybe one has to be an "old earth" creation/scientist to say the theory of the beginning of the universe was billions of yrs. Ago.