It isn't , and does not have to be.
consider the rate sun is shrinking (reversed puts surface of sun too close to earth to support life).
Also, the moon's revolution decay (ditto)
Earth's rotation, is slowing down...(reverse . would have continents formed differently)
I am being simplistic, but you get my drift (?)
Does your faith have to have billions of years???
Please note there is know way to know exact age. But we don't need a vast amount of time.
Thanks for your question
Why thank me? You ignored my question.