When did Jesus launch his public ministry?

Luke 4:16-21 NIV >**16** He went to Nazareth, where he had been brought up, and on the Sabbath day he went into the synagogue, as was his custom. He stood up to read, **17** and the scroll of the prophet Isaiah was handed to him. Unrolling it, he found the place where it is written: **18** “The Spirit of the Lord is on me, because he has anointed me to proclaim good news to the poor. He has sent me to proclaim freedom for the prisoners and recovery of sight for the blind, to set the oppressed free, **19** to proclaim the year of the Lord’s favor.” **20** Then he rolled up the scroll, gave it back to the attendant and sat down. The eyes of everyone in the synagogue were fastened on him. **21** He began by saying to them, “Today this scripture is fulfilled in your hearing.” John 2:11 NIV >What Jesus did here in Cana of Galilee was the first of the signs through which he revealed his glory; and his disciples believed in him. Mark 1:14-15 NIV >**14** After John was put in prison, Jesus went into Galilee, proclaiming the good news of God. **15** “The time has come,” he said. “The kingdom of God has come near. Repent and believe the good news!” Matthew 4 cites the same context as the initiation of Jesus' public ministry. We see that Luke presents a perfect starting point for the public ministry of Jesus in Nazareth. John, however, appears to say that Jesus started his ministry with the miracle at Cana. Matthew and Mark on their part, present an event in Galilee by which Jesus started his public life. Exactly when did Jesus launch his public ministry?