In my opinion the Bible is a great source of evidence also the best source.
It says God has always been there, and there was nothing besides him since he's self sustainable. But then he spoke the earth into existence, along the course of a week, he also created heaven.
I think since then the earth is 6-10 thousand years old. Keep in mind, he created the earth WITH age. The first humans weren't newborn, they were adults. They're first she was probably like 20, they were never 19 since they were created at 20.
So he could have made mountains with dirt and rocks that test to be millions of years old or something, when really the dirt was just one day old since it's creation.