Actually, recently I have discovered some information that may indicate that there were TWO paschal meals: one on the 14th and one on the 15th in Jerusalem. It is unclear to me at this time whether the observance was divided geographically (Galilean and Judean) or sectarian (Sadducee and Pharisee). One explanation* given for this 'dual Passover' situation was pragmatic: to make it possible for about half the Jews to bring their sacrifices to the Temple on each day (otherwise there would not be enough time/space/priests to get them all sacrificed in a single day). If this was indeed the case, then Jesus could have had a legitimate paschal meal with His Galilean disciples the night before His crucifixion and still have been sacrificed simultaneously with paschal lambs the following day (when those Judean Pharisees were going to observe Passover). It accounts for two "preparation" days as Mark and John describe (note to Bart Ehrman: you were wrong about this being an irresolvable discrepancy in your book).
Actually, Frank, we see that by Jesus' time on earth, it had become impractical for many Israelis to come to Jerusalem for passover, and originally Israel had observed passover in each family's tent. Also, most Jews bought their paschal lambs, as many of them were in non-agrarian professions by then.
Jesus' "family" at that time was His disciples, so they ate the paschal meal together. And I certainly don't believe JESUS woulda eaten the passover on the wrong day! The "two paschal meal" theory just doesn't make any sense in the face of the super-legalistic Jewish leadership of that day, who woulda had a legitimate reason for slaying Jesus had He eaten paschal on the wrong day, and who certainly would NOT have done so themselves, careful as they were to observe every jot & tittle of the OT law.
Sportzz Fanzz, we're(myself included) getting off on a tangent away from the theme of this thread, which is Dr. Gipp's "Wrong Answer Book".