On the 14th of NISAN (April 27-28) 28 AD, at evening, as the Passover Lamb was being killed, our Lord and Savior, Jesus Christ, was crucified and slain for us.  He was the Passover Lamb that year.

   About one year earlier, shortly before the Passover and Feast of Unleavened Bread in 27 AD, Jesus Christ had been water baptized by John, received holy spirit, and was then tempted for forty days in the wilderness.  He was in Jerusalem for the Passover and spoke to Nicodemus about spiritual birth as his teaching and healing ministry began.  During the first few months following he spoke about his ministry in the Synagogue at Nazareth where he began to preach the gospel about the kingdom of God:

Luke 4:17-19
   And there was delivered unto him the book of the prophet Esaias.  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 hath anointed me to preach the gospel to the poor; he hath sent me to heal the brokenhearted, to preach deliverance to the captives, and recovering of sight to the blind, to set at liberty them that are bruised,
   To preach the acceptable year of the Lord.

   Scriptural and historical evidence indicates that the acceptable year of the Lord in which all of the tremendous works of Jesus Christ that are recorded in Matthew, Mark, Luke, and John occurred was, in reality, one calendar year beginning around the Passover of 27 AD recorded in John 2:13 and ending with his crucifixion at the time of the Passover in 28 AD.

   One requirement of the law regarding the Passover Lamb was that it be a lamb of the first year.  If Jesus Christ was to be our Passover sacrifice he too had to be a lamb of the first year.  The first year cannot refer to Jesus' age as we know that he was baptized of John and began his ministry when he "began to be about thirty years of age" (Luke 3:23).  Jesus Christ was a lamb of the first year in that for a year he had been holding forth the gospel of healing and deliverance and preaching about the kingdom of God: preaching the acceptable year of the Lord.

Exodus 12:5-6
   Your lamb shall be without blemish, a male of the first year:  ye shall take it out from the sheep, or from the goats:
   And ye shall keep it up until the fourteenth day of the same month: and the whole assembly of the congregation of Israel shall kill it in the evening.

   Preparations for the Passover meal and the Feast of Unleavened bread began the first day of the month with the blowing of trumpets that signaled a new year on the Hebrew calendar.  On the tenth day of the month the lamb was selected as preparations continued.

Exodus 12:3
   Speak ye unto all the congregation of Israel, saying, In the tenth day of this month they shall take to them every man a lamb according to the house of their fathers, a lamb for an house:

   Preparations for the Passover included a requirement that all males of the house of Israel come to Jerusalem prior to the Passover and purify themselves.  During this preparation time at the end of his ministry Jesus Christ was in Bethany near Jerusalem to prepare as required by the law and it was during this preparation time that he ate the last supper with his disciples.  It was not the Passover meal; it was Jesus Christ's last supper.

John 11:55, 12:1
   And the Jews' passover was nigh at hand: and many went out of the country up to Jerusalem before the passover, to purify themselves.
   Then Jesus six days before the passover came to Bethany, where Lazarus was which had been dead, whom he raised from the dead.

   Many have said that the last supper that Jesus Christ ate with his disciples was the Passover meal.  This cannot be as the Passover meal was eaten at night on the 15th of Nisan at which time Jesus Christ was dead and buried.  This is clearly seen in the following records:

John 18:28
   Then led they Jesus from Caiaphas unto the hall of judgment; and it was early; and they [the Judeans] went not into the judgment hall [Pilate's judgment hall - a Gentile place that would leave them unclean for the Passover], lest they should be defiled; but that they might eat the passover.

John 19:42
   There laid they Jesus therefore because of the Jews' preparation day; for the sepulchre was nigh at hand.

   Both of these events, judgment before Pilate and the burial of Jesus, happened after the last supper during the preparation period and before the Passover meal which was eaten at nightfall which began the 15th of Nisan.   Jesus Christ did not keep the Passover meal with his disciples - he WAS the passover lamb that year.

   Jesus Christ was a lamb of the first year.  He preached for one acceptable year of the Lord which ended with his perfect sacrifice for us as the true Passover lamb.

A detailed study of the ministry of Jesus Christ is available in Walter J. Cummins' Scripture Consulting journal Issues 1-12: The Acceptable Year of the Lord.
A detailed study of Jesus Christ as the Passover lamb is available in Victor Paul Wierwille's book: Jesus Christ Our Passover - American Christian Press.