If I'm not mistaken, his childhood is a bit vague in the Bible. It briefly touches on it, then on his teenage years, and jumps straight into his work ministering. So as far as exact dates go pertaining to carpentering, I'm not sure you'll find a reliable answer to that question.
Luke 3:23 on the subject of preaching though says, "Now Jesus himself was about thirty years old when he began his ministry. He was the son, so it was thought, of Joseph, the son of Heli,"