First off, if we wiped the theory of evolution from everyone’s minds and burned every book ever written on evolution we would still conclude that the Earth is 4.5 billion years old. The age of the Earth is determined by geology and physics, and it has nothing to do with evolution.
Second, the first geologists to come to the realization that the Earth was millions, perhaps billions of years old, were Christians. Atheism had nothing to do with it. In fact, the evidence for an old Earth was so overwhelming in the mid 1800’s that a guy named Philip Henry Gosse wrote a book called “Omphalos: An Attempt to Untie the Geological Knot” in 1857, 2 years before Darwin published “Origin of Species”. In the book, Gosse argued that God implanted a fake geologic history into the Earth. The response wasn’t that great:
“Shall I tell you the truth? It is best. Your book is the first that ever made me doubt, and I fear it will make hundreds do so. Your book tends to prove this—that if we accept the fact of absolute creation, God becomes Deus quidam deceptor [‘God who is sometimes a deceiver’]. I do not mean merely in the case of fossils which pretend to be the bones of dead animals; but in the one single case of your newly created scars on the pandanus trunk, your newly created Adam’s navel, you make God tell a lie. It is not my reason, but my conscience which revolts here … I cannot … believe that God has written on the rocks one enormous and superfluous lie for all mankind.” --Reverend Charles Kingsley
As others have mentioned, you can continue to pretend as if geology is an atheist conspiracy going back more than 200 years, but people you witness to will see right through it. Why should they trust what you say about the Bible and God if you so willingly misrepresent known facts about geology?