As with several other issues in the Christian faith, many people are in the dark as to how many years our Lord and Saviour Jesus Christ lived during his earthly ministry. This situation need not arise as the Bible record leaves no room for doubt.
In discoursing the subject, certain facts should be borne in mind. These are facts about when Christ was born and when he was baptized. Jesus Christ was born in the seventh month of the Jews called Ethanim or Tishri which corresponds to our October. How do we know this? Zacharias the priest finished his officiation in early July; John the Baptist was conceived that very month. (1 Chronicles 24:10; Luke 1:5, 23, 24) John the Baptist was six months older than Jesus Christ and was born in April, meaning that Christ was born six months later, in October. Moreover, since Christ was conceived in January as confirmed by Elizabeth's declaration, his birth doubtless took place in the tenth month, which is October. - Luke 1:26, 27, 36, 37; 39-41, 56, 57
How then can one know that Christ lived for 33½ years on earth? When Jesus attained the age of 30, the age of maturity, as stated in the law, he was baptized by John the Baptist. (Numbers 4:3, 23; Luke 3: 21-23; Matthew 3:13-17) The month of October in that part of the world is a period of fair weather which allows people who came for baptism to be safely immersed in cold water. After the baptism, Christ was anointed with the Holy Spirit and given the commission by God to start his ministry.
That apart, God commanded the Jews through Moses to celebrate the Passover on the 14th day of Nisan or Abib, the first month of the Jewish year which corresponds to our April (Exodus 12:6-17, 23:15, Leviticus 23:4,5, etc.) With this annual celebration of the Passover feasts in the month of April in mind, we have a solid base to count the years Jesus Christ lived on earth after his baptism in the month of October when he was 30 years old. The first feast of Passover Christ celebrated after his baptism was that recorded in John 2:13-25. While at Jerusalem for the occasion he found in the temple those that sold oxen, sheep and doves, and the changers of money. He made a whip and drove them all out of the temple. Counting from November the first month after his baptism to April when the first Passover feast came up we would have six months. This therefore means that at this time Jesus Christ had attained the age of 30 years and six months.
The second feast of Passover celebrated by Christ after his baptism was recorded in the Book of John Chapter 5. On this occasion, Apostle John reports that Christ went to Jerusalem and found "a great multitude" of sick people "waiting for the moving of the water". There at the pool of Bethesda Jesus Christ cured a man who "had an infirmity 38 years". (John 5:1-9) By this second Passover celebration after his baptism Jesus Christ can be seen to have attained the age of 31 years, six months or one and a half years of his ministry.
Christ's celebration of the third Passover feast after his baptism was that which followed his miraculous feeding of 5,000 people with only five barley loaves and two fishes. (John 6:1-14) At this time Christ had already attained the age of 32 years six months or two and a half years of his ministry. Jesus Christ celebrated his fourth and last Passover before his crucifixion (Luke 22:1-14; John 11:55; John 13:1). He arrived Bethany six days before the Passover feast (John 12:1) It was then Mary poured an alabaster box of precious ointment on his head as he sat at meat at the house of Simon the leper. (Matthew 26: 2-13, 17-29: Mark 14:3-9; John 12:1-8) At this time, the Jews came to see Jesus and Lazarus whom he had raised from the dead and if possible to kill Lazarus. (John 12:9-11) This period was also marked by His triumphant entry to Jerusalem as the future king of God's Kingdom. (John 12:12-19) Firstly, when all the Jews had gathered at Jerusalem for the feast, the chief priests and Pharisees gave order that any one who found Christ should report so that he could be arrested. (John 11:55-57) It was during this occasion, he was arrested, put on trial and crucified - Matthew 26: 2,18,26-56; John 18:1-14
To further show that it was at this fourth Passover after his baptism Christ was killed. St John reports that before the very day of the feast Jesus knew that "his hour was come that he should depart out of this world unto the Father". (John 13:1) After eating the last supper with his Apostles, and just before he was arrested he took water in a basin and washed his disciples' feet. (John 13:2-16) On the eve of the Passover (the day of preparation) when Jesus was brought to Pontius Pilate, the Jews who were aware of the law of God about self-purification in "preparation" for the celebration, refused to enter the judgment hall, "lest they should be defiled: but that they might eat the Passover". (Chapter 18:28, 29, 19:14) This, no doubt seals the fact that Jesus Christ was actually killed during this 4th Passover, celebrated always in April, and his age then stood at 33 years, six months.
From the above biblical proofs, it is evident that our Lord and Master Jesus Christ, lived on this earth for 33½ years. His 33rd birth anniversary took place in October and six months later, in April, he was killed.