The most widely accepted answer is, 3 ½ years. Another school of thought is that, according to the Jewish feast cycles; it could have only been 1 year from His springtime baptism by John during Passover, to His following springtime crucifixion at the following Passover.
The latter belief system compresses the time-line too quickly according to the book of John. Jesus had to have attended at least two annual Passovers throughout his public ministry as evidenced in (John 2:13) and (John 6:4) and a third and last Passover where the order was declared to seize Jesus which lead to His crucifixion; given by the chief priests and Pharisees in (John 11:55-57).
Satan wants man to get caught up in the little things of scripture to hide the preeminent truths pointing the way of salvation.
Satan’s sole desire is to be like God and take God’s place. (Isaiah 14:13-15) If he can get people to quibble over the small stuff, the less they will learn and the more power he gains.
Ignorance of the nature of both God and Satan leads to confusion.
This confusion is the cesspool of darkness blinding the minds of those who argue the trivial or irrelevant essay of scriptures.
But even if our gospel is veiled, it is veiled to those who are perishing, whose minds the god of this age has blinded, who do not believe, lest the light of the gospel of the glory of Christ, who is the image of God, should shine on them. (2 Corinthians 4:3-4)
Bone to Pick
There is still yet another bone of contention with which the debate is stirred. This being, when did He start and what did He preach?
Now Jesus Himself began His ministry at about thirty years of age, being (as was supposed) the son of Joseph, the son of Heli, (Luke 3:23)
Now when Jesus had heard that John was cast into prison, he departed into Galilee; And leaving Nazareth, he came and dwelt in Capernaum, which is upon the sea coast, in the borders of Zabulon and Nephthalim: That it might be fulfilled which was spoken by Esaias the prophet, saying, The land of Zabulon, and the land of Nephthalim, by the way of the sea, beyond Jordan, Galilee of the Gentiles; The people which sat in darkness saw great light; and to them which sat in the region and shadow of death light is sprung up. From that time Jesus began to preach, and to say, Repent: for the kingdom of heaven is at hand. (Matthew 4:12-17)
Then Jesus returned in the power of the Spirit to Galilee, and news of Him went out through all the surrounding region. And He taught in their synagogues, being glorified by all. Jesus Rejected at Nazareth So He came to Nazareth, where He had been brought up. And as His custom was, He went into the synagogue on the Sabbath day, and stood up to read. And He was handed the book of the prophet Isaiah. And when He had opened the book, He found the place where it was written: “The Spirit of the Lord is upon Me, Because He has anointed Me To preach the gospel to the poor; He has sent Me to heal the brokenhearted, To proclaim liberty to the captives And recovery of sight to the blind, To set at liberty those who are oppressed; To proclaim the acceptable year of the Lord.” Then He closed the book, and gave it back to the attendant and sat down. And the eyes of all who were in the synagogue were fixed on Him. And He began to say to them, “Today this Scripture is fulfilled in your hearing.” So all bore witness to Him, and marveled at the gracious words which proceeded out of His mouth. And they said, “Is this not Joseph’s son?” (Luke 4:14-22)
Some people just can’t agree on whether Jesus started off by preaching the gospel to the poor or screaming Repent! This depends upon which bandwagon you are traveling with.
The prosperity groupies side with Luke while the evangelical groupies prefer Matthew’s Repent. Why can’t it be both? Since one obviously can’t enjoy the perks of salvation without repentance first!
Before or After Jail?
At least everyone seems to agree that it began after Jesus found out that John had been arrested and imprisoned; Right? Well…. this seems to depend on whether or not you are talking about a private or public ministry.
Here is a verse showing us that; Jesus had to be preaching or teaching something that convinced people to become His disciples before John went to jail.
After these things Jesus and His disciples came into the land of Judea, and there He remained with them and baptized. Now John also was baptizing in Aenon near Salim, because there was much water there. And they came and were baptized. For John had not yet been thrown into prison. (John 3:22-24)
Here is another which boast a higher conversion rate of discipleship followers than John the Baptist.
Therefore, when the Lord knew that the Pharisees had heard that Jesus made and baptized more disciples than John (though Jesus Himself did not baptize, but His disciples), (John 4:1-2)
What’s He Doing?
Let us not forget about Jesus’ escapades in Jerusalem when He was just 12 years old. Jesus had been going there with His family every year to the 8 day Feast of the Passover. He certainly learned where to go and what to do.
He undoubtedly made acquaintances and friends after so many yearly vacation pilgrimages. What escapades might a young Boy Jesus filled with wisdom do?
So when they had performed all things according to the law of the Lord, they returned to Galilee, to their own city, Nazareth. And the Child grew and became strong in spirit, filled with wisdom; and the grace of God was upon Him.
His parents went to Jerusalem every year at the Feast of the Passover. And when He was twelve years old, they went up to Jerusalem according to the custom of the feast. When they had finished the days, as they returned, the Boy Jesus lingered behind in Jerusalem. And Joseph and His mother did not know it; but supposing Him to have been in the company, they went a day’s journey, and sought Him among their relatives and acquaintances. So when they did not find Him, they returned to Jerusalem, seeking Him. Now so it was that after three days they found Him in the temple, sitting in the midst of the teachers, both listening to them and asking them questions. And all who heard Him were astonished at His understanding and answers. So when they saw Him, they were amazed; and His mother said to Him, “Son, why have You done this to us? Look, Your father and I have sought You anxiously.”
And He said to them, “Why did you seek Me? Did you not know that I must be about My Father’s business?” But they did not understand the statement which He spoke to them.
Then He went down with them and came to Nazareth, and was subject to them, but His mother kept all these things in her heart. And Jesus increased in wisdom and stature, and in favor with God and men. (Luke 2:39-52)
How Long is That?
This brings us full circle back to the question. How long did Jesus preach? The real answer is… Since before the dawn of creation onward forever.
who, being in the form of God, did not consider it robbery to be equal with God, but made Himself of no reputation, taking the form of a bondservant, and coming in the likeness of men. (Philippians 2:6-7)
And the Word became flesh and dwelt among us, and we beheld His glory, the glory as of the only begotten of the Father, full of grace and truth. (John 1:14)
“Behold, the virgin shall be with child, and bear a Son, and they shall call His name Immanuel,” which is translated, “God with us.” (Matthew 1:23)
This is the whole purpose behind Jesus becoming a baby swaddled and lying in a manger. God’s Word became the flesh known as Jesus (Immanuel) to become Christ for All of Mankind.
Even His birth was a sermon of multitudes paving the way for His love and plan of salvation. Jesus has been preaching and teaching since time immemorial. Beyond the ancient of days, long before the dawn of creation because: He loves You so.
And she brought forth her firstborn Son, and wrapped Him in swaddling cloths, and laid Him in a manger, because there was no room for them in the inn.
Now there were in the same country shepherds living out in the fields, keeping watch over their flock by night. And behold, an angel of the Lord stood before them, and the glory of the Lord shone around them, and they were greatly afraid. Then the angel said to them, “Do not be afraid, for behold, I bring you good tidings of great joy which will be to all people. For there is born to you this day in the city of David a Savior, who is Christ the Lord. And this will be the sign to you: You will find a Babe wrapped in swaddling cloths, lying in a manger.”
And suddenly there was with the angel a multitude of the heavenly host praising God and saying:
“Glory to God in the highest,
And on earth peace, goodwill toward men!”
Merry Christmas to All and to All get Life. (John 14:6)