26:17 the first day of Unleavened Bread. The day of preparation for Passover, presumably 14 Nisan (the first month of the Jewish calendar). Jesus celebrated Passover that evening, 15 Nisan, and was crucified the next afternoon. The Gospel of John seems to present Jesus as crucified on the day before Passover (John 18:28; 19:14, 31), making the Lord’s Supper not a Passover meal.
Calvin understood Preparation Day to be the day before Passover, and argued that the Jews according to some traditions combined the Passover with the weekly Sabbath (John 19:14 note). Then Matt. 27:62 would refer to the Preparation Day observed by the Jewish leadership. There is some difficulty, however, in seeing how Jesus’ disciples could have had their lamb slaughtered in advance of the official schedule, and Mark 14:12 clearly indicates that Jesus arranged for Passover on the day when the lambs were customarily slaughtered. Whatever the solution, Matthew clearly identifies the meal that Jesus ate with His disciples on the eve of His crucifixion as the Passover meal.