Even a quick and superficial reading of the four gospels reveals some obvious similarities and differences. While Matthew, Mark, and Luke share many stories in common — indeed, much of it said in the same words — John has a great deal of material that is quite different from the other three (known collectively as the “Synoptic” gospels, or simply, “the Synoptics”).

That’s particularly true as we come to the so-called Last Supper. All four gospels tell a story about Jesus’ last meal with his disciples, just before his betrayal, arrest, and crucifixion. But only John tells us the Jesus washed his disciples’ feet. Only John records the long discourse and prayer that followed.

And there’s another difference that’s easy to miss unless you read the gospels more closely, side by side: while Matthew, Mark, and Luke portray the Last Supper as a Passover meal, John seems to insist that it was not.

John opens his story by declaring that it was “before the festival of the Passover” (13:1, NRSV). That’s a little ambiguous, of course. But John 18:28 makes it clear that even after Jesus had been arrested, his opponents had not yet eaten the Passover meal, and 19:14 declares that Pilate passed judgment on the day of preparation for the Passover.

Many solutions have been proposed to this little conundrum. Some argue that John has altered the timeline to make a theological point: Jesus was crucified at the same time that the Passover lambs were being slaughtered. Others suggest that Jesus decided to have the Passover meal early, because he knew what was going to happen to him. Still others suggest that Galileans may have celebrated on a different day, or by a different calendar.

Short of asking John directly, we may never know. (And by that time, I’m guessing we won’t care.)

But we can’t shy away from such apparent contradictions. John’s gospel is deeply theological; it is not written as a blow-by-blow account of everything Jesus said and did. Right from the very first chapter, John has wanted us to know Jesus as the Lamb of God, and at every point, he has organized his stories around the Jewish festivals, Passover in particular.

Whatever the truth about the Supper itself, I believe John wants us to understand the story of Jesus against the backdrop of the story of the Passover. Millions thronged Jerusalem to celebrate the festival, unaware that Jesus himself would be their Passover sacrifice.

It’s the terrible irony of religious practice performed in God’s name, but oblivious to what God is actually doing.

May we never be guilty of the same.