The account in the Book of Genesis is in logical, not chronological, order. The writer groups together similar works of creation, for the easier understanding of a primitive people. The Church has not made any positive definition of the way in which the Biblical account of Creation is to be interpreted. Neither Revelation nor Science gives a definite answer to the question concerning the age of the world. Geologists assert that long periods of time were necessary for the formation of the various strata of the earth's surface.
Astronomers assert that some stars are a million light-years from the earth.
A Catholic is free to hold on this point whatever he believes is a sound and scientific conclusion. The estimates of scientists vary.