Some think that the young earth/old earth debate is between Christians and evolutionists. But the truth is many evangelical Christians believe in an old earth. Those that support a young earth normally estimate the age to be between 6000 and 10000 years old. Others allow for millions and sometimes billions of 
years. Those who argue for a young earth connect their view to a literal interpretation of Genesis 1 &2, along with the laws regarding the seventh day in Exodus 20. You might find it interesting, however, to know that the old earthers claim the same basic hermeneutic (basis for Bible Interpretation). They insist the language of the days of creation could honestly allow for the billions of years view to be accurate also. The age of the earth is not a test of true Christianity. Sincere believers are on both sides of the issue. Neither view can be proven scientifically as far as we know. The fact of creation is a much more important issue and the common enemy of all true believers is naturalistic evolution, not the “how” of God’s creation as expressed in Genesis 1 & 2.
However, with that said, I find it less cumbersome to subscribe to the younger earth position with a few personal variances. I’ll give you my reasons for believing this and you can disagree with me and we can still remain friends. ( I hope!) The normal use of the word “day” in Genesis refers to a 24 hour period. Whenever days are numbered in the Old Testament they always refers to 24 hour days. The use of “Evening and Morning” in the creation accounts supports the idea of a 24 hour day. According to Exodus 20, the work week was to be followed by a day of rest. It’s called the Sabbath. This illustrates that the work week parallels God’s creative work week of six literal days of creation after which he rested. However, I must admit that I’ve heard good biblical arguments that refute each of my reasons. So, we can dialogue about this issue and continue as brothers & sisters in Christ.
There is no necessary conflict between Genesis and the belief that the universe is millions or even billions of years old. Indeed, of all the ways of interpreting Genesis 1–2, only those who say Genesis is simply a myth hold to a totally incompatible view since they reject the Bible as providing literal information about the origins of our universe.
Chuck
“In the beginning, God created the heavens and the earth.” Genesis 1:1