The accepted answer on How long was Jesus in the tomb? would only have been possible if the Last Supper was not the Passover meal, which I had always thought it was. Was the Last Supper in fact not the Passover meal?
My new understanding of the Last Supper is mostly based on the information at http://www.therefinersfire.org/celebrating_passover.htm.
The key verses which indicate that Christ was actually crucified on the day before the Passover feast are John 18:28 and John 19:14.
The day of preparation would be when they slaughter the Passover lamb, which would then be eaten that night.
Two things are clear from scripture:
There are a number of possible reconciliations of this. Some speculate that Jesus was a part of a minority Jewish sect that celebrated Passover on a different day. Others that he celebrated Passover a day early because he knew he wouldn't be able to do it on the right day (I don't know what Jewish Law would have said about that, but Jesus was never one to get hung up on legal technicalities).
The simple answer is that they were not. This is certainly not obvious from the Gospel of John, or even the Gospel of Matthew or Mark, but it is evident when we closely read the Gospel of Luke.
In Luke 22:7, it is written,
(Note: This "day of Unleavened Bread" refers to Nisan 14, as the Jews reckoned even this day, although properly "the Passover" (cp. Exo. 12:6), as the first day of the Feast of Unleavened Bread. In fact, they often called the entire "Feast of Unleavened Bread" by the name "Passover."1)
On Nisan 14, Jesus commands Peter and John to "go prepare the Passover so we may eat" (Luke 22:8). Then, they went to Jerusalem and found the man Jesus instructed them about (cp. Luke 22:10-12), "and they prepared the Passover" (Luke 22:13).
In Luke 22:14, it is written,
So, Jesus and the twelve apostles reclined and began to eat the Passover seder.2 He says to the twelve, "I have earnestly desired to eat this Passover with you before my suffering" (Luke 22:15). Then he says to the twelve, "I will not eat of it anymore until it be fulfilled in the kingdom of God." But, that Jesus ate then and there, it is certain (cp. Matt. 26:21; Mark 14:18).
Jesus then receives a cup, gives thanks to the Father, and says to the twelve, "Take this [cup] and divide it among yourselves" (Luke 22:17). Based on these words, it is arguable that Jesus himself drank from the cup; however, it seems likely that he did.3
Now, at this point, Jesus had been eating the Passover seder with the twelve, and he drank a cup of wine and distributed to his apostles. After this, note the following:
In Luke 22:19, it is written,
Luke 22:19 demonstrates the commencement of the Last Supper.
In Luke 22:20, it is written,
Notice that Jesus had already distributed a cup to the twelve (Luke 22:17) during a previous meal, and after eating that meal (μετὰ τὸ δειπνῆσαι), he takes bread (Luke 22:19) and then another cup (Luke 22:20)! This is the evidence that two meals are involved. Two cups; two meals. The first meal was the Passover seder; the second meal is the Last Supper. They are not the same meal. The Passover seder was not the Last Supper.
John Gill on Luke 22:19,
Count the cups...it's only in Luke's Gospel, but it's there.
2 It was custom to recline while eating the Passover seder. See Jerusalem Talmud, Tractate Pesachim, Chapter 10, Folio 68b, Halakha 1: ולפי שדרך עבדים להיות אוכלין מעומד וכאן להיות אוכלין מסובין להודיע שיצאו מעבדות לחירות, that is, "Because it is the custom of slaves to eat standing, here [it is the custom] to eat reclining to proclaim that they have gone out from slavery to freedom."
3 See Meyer's commentary on Luke 22:17.
4 The phrase μετὰ τὸ δειπνῆσαι is the preposition μετὰ, meaning "after," followed by the substantive infinitive τὸ δειπνῆσαι, meaning "dining" or "eating (a meal)." It simply refers to eating a meal. Although the KJV translates it simply as "supper," as though it was a noun, it should not be assumed that this "supper" is the "Last Supper," as many may erroneously assume. BDAG defines the verb as, "to eat a meal (without ref. to time of day or type of food), eat, dine."