Bible readers throughout history have noticed discrepancies in the Gospel accounts, and this often leads people to question the Bible's veracity entirely. For example, Matthew, Mark and Luke all state the Last Supper was a meal marking the start of the Jewish festival of Passover. John, by contrast, says that it took place before the Passover began. Whatever you think about the Bible, the fact is that Jewish people would never mistake the Passover meal for another meal, so for the Gospels to contradict themselves about this is really hard to understand. The eminent biblical scholar F.F. Bruce once described this problem as "the thorniest problem in the New Testament."
The Gospels also do not seem to allow enough time for all the events they record between the Last Supper and the Crucifixion, whilst indicating that Wednesday was a "missing day" on which Jesus did nothing. Scholars have literally rushed around Jerusalem with a stop-watch to see how the large number of events recorded in the Gospels could have fit between the Last Supper on Thursday night and the Crucifixion on Friday morning. Most conclude that it is impossible.
However, it turns out that there is a very simple solution to these problems: If you move the Last Supper to Wednesday, instead of Thursday, the Gospels are actually in remarkable agreement, and can be read as a reliable record.
What really happened in Jesus' last week?
In my new book, The Mystery of the Last Supper, I use science and historical reconstruction to take a closer look at the inconsistencies in the Gospel accounts of the final days of Jesus. Essential to this task was the use of different calendars. The Dead Sea Scrolls reveal that there were a number of different Jewish calendars in use in Israel in the first century A.D., and so different Jewish groups celebrated Passover on different days. We have a similar situation today with the date of Easter: Catholics and Protestants celebrate Easter on a different date from Greek and Russian Orthodox Christians because they calculate the date of Easter using different calendars (Gregorian and Julian, respectively).
In his description of the Last Supper, John uses the official Jewish calendar, in which the Last Supper was before the date of the official Passover. However, I suggest that Jesus chose to hold his Last Supper on the date of Passover in a different Jewish calendar, which is what Matthew, Mark and Luke report. So all four Gospels in fact agree!
I am not the first person to suggest that Jesus might have been using a different calendar. Most recently, the Pope proposed in 2007 that Jesus might have used the solar calendar of the Qumran community, who were probably a Jewish sect called the Essenes. But when the date of Passover is calculated using this calendar, it would have fallen a week later, after both Jesus' death and resurrection.
I have worked with an expert astronomer to investigate, for the first time, the possibility that a third Jewish calendar was in use in the first century A.D. The official Jewish calendar at the time of Jesus' death was that still used by Jews today: a lunar system in which days run from sunset to sunset. This was developed during the Jewish exile in Babylon in the sixth century B.C. Before that, however, the Jews had a different system. This is referred to in the Book of Exodus, in the Old Testament, when God instructs Moses and Aaron to start their year at the time of the Exodus from Egypt.
There is extensive evidence that this original Jewish calendar survived to Jesus' time. It was used by groups such as the Samaritans, Zealots, some Galileans and some Essenes. Under this pre-exilic calendar, Passover always fell a few days earlier than in the official Jewish calendar, and the days were marked from sunrise to sunrise, not sunset to sunset.
Using our reconstruction of this calendar we can see that in A.D. 33, the year of the Crucifixion, the Passover meal was on the Wednesday of Holy Week. From the clues they give, it's clear that Matthew, Mark and Luke all used the pre-exilic calendar in their description of the Last Supper as a Passover meal, whereas John uses the official calendar in which the Last Supper was before the Passover.
What does this mean for our celebration of Easter?
Holy Thursday is the well-known day on which Christians annually commemorate the Last Supper of Jesus. But my research shows that we should really be celebrating this on the Wednesday of Holy Week. A Wednesday Last Supper with the Crucifixion on Friday also allows just the right amount of time for all the events the Gospels record between the Last Supper and the Crucifixion.
Today, about half of the churches in the world use unleavened bread in their weekly or monthly celebration of the Last Supper, because they believe it was a Passover meal, and half use leavened bread, because they believe it was before the Passover meal. I have shown that everyone is right! The Last Supper was before Passover in the official Jewish calendar (used by John), but it was the Passover meal in the earlier original Jewish calendar that Jesus chose to use for his Last Supper (described by Matthew, Mark and Luke).
We celebrate Christmas on a fixed date each year: Dec. 25. However, Easter is a moveable feast: the date of Easter Sunday changes every year, according to a complicated formula, and can range from March 23 to April 25. For those who would like a more fixed date for Easter, my research suggests that Easter Sunday should be the first Sunday in April.
Finally, why did Jesus choose to hold his Last Supper at Passover time according to the pre-exilic calendar? I suggest it was because this original Jewish calendar was the one the Old Testament says was used by Moses to celebrate the very first Passover in Egypt. The Gospels are full of examples of Jesus presenting himself as the new Moses. Jesus was therefore holding his Last Supper on the exact anniversary of the first Passover of Moses, thus proclaiming that he was the new Moses, instituting a new covenant and leading his people out of slavery into a new life. Jesus then died just as the Passover lambs were being slain, according to the official Jewish calendar. These are deep, powerful symbolisms, which are based on objective, historical evidence. Far from being incompatible, as many scholars make them out to be, here science and the Bible work hand-in-hand to show that all four Gospels are in remarkable agreement about Jesus' final days.