I came across this great article on the idea of millions of years. It is a little bit of a read but some great foundational information on the topic. I found it very insightful. Hope you enjoy it... https://answersingenesis.org/theory-of-evolution/millions-of-years/where-did-the-idea-of-millions-of-years-come-from/
Where Did the Idea of “Millions of Years” Come From?
Today, most people in the world, including most people in the Church, take for granted that the earth and universe are millions and millions of years old.
answersingenesis.org