I. The Last Supper Was Not the Jewish Passover.
John gives five distinct intimations of the date:
(1)) "Now before the feast of the passover" (Pro de tes heortes tou pascha; John 13:1). This shows that the washing of the disciples' feet, and the discourses at the Last Supper were before the Passover.
(2) "Buy what things we have need of for the feast" agorason hon chreian echomen eis ten heorten; John 13:29). This shows that the Supper (daiphon) was not the Passover feast [@heorten).
(3) "They lead Jesus therefore from Caiaphas into the Pretorium; and it was early; and they themselves entered not into the Pretorium, that they might not be defiled, but might eat the passover" (hina phagosin to pascha; John 18:28). This was after the Supper, early on the day of crucifixion, before the Passover.
(4) "Now it was the Preparation of the passover: it was about the sixth hour" (en de paraskeue tou pascha; John 19:14). This again shows conclusively that the Passover was not yet eaten. Jesus is before Pilate; it is the day of the crucifixion, and after the Last Supper.
(5) "The Jews therefore, because it was the Preparation, that the bodies should not remain on the cross upon the sabbath (for the day of that sabbath was a high day)," John 19:31, etc. Here we have again a reference to the Preparation (paraskeue tou pascha), and also to the Sabbath which, in this case was a "high day" (en gar megale he hemera ekeinou tou sabbatou). This shows that the Passover was eaten on Friday evening after sunset on the 15th of Nisan at the beginning of the Jewish Sabbath. Whenever the Passover fell upon the Sabbath, that Sabbath was a "high day."
Christ is our Passover: died at the time the Passover lamb was slain, hence, after the Last Supper. (1) Christ died at the time the Passover lamb was slain on Friday afternoon, the 14th of Nisan, and thus became Our Passover (1 Corinthians 5:7), "For our passover also hath been sacrificed, even Christ." (2) Jesus, the "Lamb of God" (John 1:29) corresponds to the Passover lamb (Exodus 12:3). "Without blemish" (Exodus 12:5) = Jesus, "who did no sin" (1 Peter 2:22-24). The blood of a lamb sprinkled upon houses (Exodus 12:7,13) corresponds to salvation by the blood of Jesus (1 John 1:7-9). (3) Jesus arose the third day and became "the first-fruits of them that are asleep" (1 Corinthians 15:4,20,23). The resurrection was on the third day. The sheaf, or first-fruits, was gathered on the 17th of Nisan. Therefore Jesus must have died on the 14th of Nisan, when the Passover lamb was slain; hence, after the Last Supper.
All the early traditions, both Jewish and Christian, agree that Jesus was crucified on the day of Preparation of the Passover, and they distinguish between the Passover and the Last Supper which was eaten the evening before the Jewish feast.