When did John find out Jesus was the Messiah?

Matthew 11:2-3; Luke 7:18-22; and John 1:29-34

In prison (Matthew 11:2,3) - "Now when John in prison heard of the works of Christ, he sent word by his disciples, 3and said to Him, "Are You the Expected One, or shall we look for someone else?"
In prison (Luke 7:18-21) - "And the disciples of John reported to him about all these things. 19And summoning two of his disciples, John sent them to the Lord, saying, "Are You the Expected One, or do we look for someone else?" 20And when the men had come to Him, they said, "John the Baptist has sent us to You, saying, ‘Are You the Expected One, or do we look for someone else?’" 21At that very time He cured many people of diseases and afflictions and evil spirits; and He granted sight to many who were blind."
While baptizing (John 1:29-31) - "The next day he *saw Jesus coming to him, and *said, "Behold, the Lamb of God who takes away the sin of the world! 30"This is He on behalf of whom I said, ‘After me comes a Man who has a higher rank than I, for He existed before me.’ 31"And I did not recognize Him, but in order that He might be manifested to Israel, I came baptizing in water."

Matthew, Mark, and Luke are known as the synoptic gospels. Synoptic means "similar." They are very similar in their approach to writing about Jesus. They are more chronological than John is and contain a majority of common information. The intent of the Gospel of John was not to present a detailed chronological account of Jesus' life. Rather, the intent was to demonstrate that Jesus is the Son of God (John 20:31). John is thematic in emphasis and he brings out those issues that demonstrate Christ's divine nature (John 1:1,14;8:24,58; 10:30-33; 20:28).

When we read the accounts of the Synoptic Gospels, we see that they mesh very well. John, on the other hand, ignores the details of the chronology and simply presents Jesus as the Christ, picking and choosing the issues in Christ's life in order to demonstrate his goal. For example, John doesn't even mention that John the Baptist was arrested as do the other gospels (Matt. 4:12; Mark 1:14; Luke 3:19-20). Why? It isn't the intent of John to present the chronological events about John the Baptist. It is meant to convince people that Jesus is the Son of God (John 20:31). Therefore, what we see in John is a synopsis of the prophetic revelation of God regarding Jesus as the Lamb of God who takes away the sins of the world. John, therefore, summarizes Jesus' baptism account in order to portray Him as the Christ.

Strictly speaking, if we were to force a chronological harmony of Matthew, Luke, and John, we would see something like the chart below.

Event	Matthew	Luke	John 1
Jesus comes to John. John says Jesus is the Lamb of God.	Matt. 3:13, Then Jesus *arrived from Galilee at the Jordan coming to John, to be baptized by him.		"The next day he saw Jesus coming to him, and said, "Behold, the Lamb of God who takes away the sin of the world! 1:30 "This is He on behalf of whom I said, ‘After me comes a Man who has a higher rank than I, for He existed before me.’ 1:31 "And I did not recognize Him, but in order that He might be manifested to Israel, I came baptizing in water." 1:32 And John bore witness saying, "I have beheld the Spirit descending as a dove out of heaven, and He remained upon Him. 1:33 "And I did not recognize Him, but He who sent me to baptize in water said to me, ‘He upon whom you see the Spirit descending and remaining upon Him, this is the one who baptizes in the Holy Spirit.’ 1:34 "And I have seen, and have borne witness that this is the Son of God."
Jesus is baptized	3:16 And after being baptized, Jesus went up immediately from the water; and behold, the heavens were opened, and he saw the Spirit of God descending as a dove, and coming upon Him,
John is arrested	4:12 Now when He heard that John had been taken into custody, He withdrew into Galilee;	3:20 he added this also to them all, that he [Herod] locked John up in prison.
John in prison heard of Christ's works	11:2 "Now when John in prison heard of the works of Christ, he sent word by his disciples,	7:18 "And the disciples of John reported to him about all these things.
"Are you the One?	11:3 and said to Him, "Are You the Expected One, or shall we look for someone else?"	7:19 And summoning two of his disciples, John sent them to the Lord, saying, "Are You the Expected One, or do we look for someone else?" 20 And when the men had come to Him, they said, "John the Baptist has sent us to You, saying, ‘Are You the Expected One, or do we look for someone else?’"