According to what GOD has revealed in HIS HOLY WORD, the entire universe is unlikely to be over 12000 years old. That is arrived with a possible hint at one day equalling one thousand years or visa versa. I tend to accept that the universe is likely no more than 6000 earth years old. The problem is that GOD saw fit to qualify HIS WORD with "evening and morning" being the defining of the day. Wherever it is used in Hebrew, it always means an approximate 24 hour period.
I am a Christian. I believe the Bible is true, but I don't believe the whole thing is literal. If you will notice, Jesus spoke to people in parables when he taught them. I assume that if Jesus spoke in parables then the prophets of the OT spoke and wrote with some parables, too. When the creation story and Adam and Eve stories were passed on by word of mouth, they were apparently spoken in a symbolic form. That is my opinion and the way I interpret it.
Even if you don't agree with this, I think it deserves a little thought.