Regardless of what man claims, this earth is not young... However, God had Peter pen exactly how God counts time ... IIPeter 3:8 But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day.
Peter also describes that flood of Genesis 1:2 ... in what Peter calls (II Peter 3: 5 For this they willingly are ignorant of, that by the word of God the heavens were of old, and the earth standing out of the water and in the water:
I would encourage you to read the rest of 2 Peter 3. Perhaps you will see why you are misusing that verse. God is not some old foolish man that has an issue counting his days apart.... ironically, it is exactly the opposite.