I don’t know the age of the earth, but I do believe that after it was created in Genesis 1:1, there was a spiritual rebellion starting with Lucifer which brought about a judgment leaving the earth without form and void (Genesis 1:2 compare Jeremiah 4:23). Isaiah 14:12-14 seems to take place on the earth. There were no physical creatures created yet, no dinosaurs or humans. After God put down that rebellion he made the earth and the things in it in 6 literal days – Genesis 1:5 & Exodus 20:11. From that point is has been about 6,000 years.