There is a gap of about 18 years before he began his ministry but he only became "fully charged" after his baptism by St John the Baptist when he had the vision of the Holy Spirit descending upon him in the river Jordan. At that point he knew what his mission was. My guess is spent some time travelling around or was part of some kind of monastic community as people asked if he was "Josephs son" as though they hadn't seen him in some years. There accounts that he spent time in his youth in Cornwall or India but I'd take that with a pinch of salt.
Come all ye faithful joyful and triumphant.
