It is perhaps useful, at the start of our Holy Week, to look at the chronology of what happens, in Mark (and with him, Mt and Lk) and in John. It is not the same in these two gospel traditions.
In Mark, what we know as the ‘Palm Sunday entry to Jerusalem’ has no specified date. [Indeed, some have suggested that it might be at the feast of Tabernacles, not at the start of Passover week.] But two days before Passover, there is a plot against Jesus, an anointing of Jesus, and an ‘expression of interest’ between Judas and the High Priests. Then, on the afternoon before Passover began, when the priests at the temple sacrificed the lambs, the disciples prepared for the last supper. In Mark, it is a Passover Meal. The time is the 15 Nisan, after sunset, in the evening that introduced that day. [Note that Jewish days start from what we would see as the ‘previous’ evening: they go from just after sundown to the next sunset.] At that meal, Jesus gives us the Eucharist. Then, on that night, after the meal, he goes to Gethsemane – possibly/probably on his way back to Bethany – it was a halfway stop on that road. He is arrested there. Everything that follows – the arrest, the trial and sentencing to death for blasphemy by the Jewish high court, the transfer to Pilate on the different charge of sedition, the Roman proceedings leading to crucifixion – occurs on the Passover festival. [The chief priests, sticklers for legal minutiae, spend the whole night and day engaged in forbidden activities on a feast day.] Jesus goes to an unofficial and then formal Sanhedrin ‘trial’ (during which the denials of Peter occur), and then on to the trial before Pilate (after which is the death of Judas). This takes all night. At 9 o’clock on the next (Friday) morning, still by Jewish counting the 15 Nisan, he is crucified. From 9 to Noon on that day, there is darkness everywhere. Jesus dies at noon. In the late afternoon of that same day he is (hastily) buried – before sundown.
The sequence, and the dating, is different in John. Jn antedates everything by 24 hours. The plot is ‘near Passover’. The anointing is ‘six days before Passover’. The entry into Jerusalem follows these events, ‘the next day’(Jn12,12) There is no mention of preparation for the last supper. The supper is not a Passover Meal, and it occurs on the evening preceding the evening in which the Passover Meal had to take place. The arrest follows. Jesus is simply interrogated by the former high priest Annas. There is no Jewish blasphemy trial. In the morning, without the accused being present, the chief priests convene and decide to deliver Jesus to Pilate (on the 14th Nisan). They refuse to enter the palace so as not to be defied and so barred from eating Passover that evening. The trial before Pilate continues until noon. He is then crucified, and dies about 3 in the (Friday) afternoon.
It would be good to know ‘who is correct’ here, that is, what ‘really’ happened and ‘exactly when’, and it is nearly impossible to know. All agree that Jesus was crucified on a Friday afternoon and that the tomb was discovered on the following Sunday morning. Beyond that, it is good to admit that we know for sure rather less than more about it all.
We don’t know for sure on what year the 14/15 Nisan (in the Jewish calendar) fell on a Thursday evening/Friday. We don’t even know for sure when the full moon (the Passover one) was visible in Palestine around those years. So it is not clear what day of the week, by our counting, was Passover in the year that Jesus died. Astronomical records indicate that in c.e.27 Passover would have been from Thursday evening to Friday. In c.e .30 and c.e. 33 Passover was from Friday evening to Saturday. The term ‘Preparation Day’ was used among Jews throughout this time, but it is not clear whether it refers to a preparation day before the weekly Sabbath, or a preparation day before the Passover – obviously, if Passover fell on a Sabbath, the preparation day would be the same.
It has also been suggested that some Jewish groups used a calendar peculiar to their groups, and that in one of those calendars Passover may have begun on Tuesday evening, not Thursday.
We don’t know these details, and we don’t need to know them, much as we would like to. Holy Week isn’t about improving our records. It’s about improving our own record!
But – any historian familiar with Judaism must realize that the Markan (Synoptic) timetable is impossible. The two trials and the crucifixion could not have taken place on Passover day. So historians usually feel bound to adopt the Johannine timetable. Whether Jn is completely ‘right’ is another matter…but he avoids the ‘wrongness’ of the Markan account.
Then some historians try to harmonize the two accounts. They would like to have it both ways. [Each account is coherent in itself, but when you try to put them together they lose that coherence.] They transfer details from the Synoptic story (that are missing from Jn), including the Jewish trial, to the day before Passover. But they are unwilling to give up thinking about the last supper as a paschal meal – they like to think, as Mark obviously does, that Jesus and the disciples sang the Hallel (to conclude the Passover meal) en route to Gethsemane.
It has been suggested, reasonably enough, that all that the early believers knew was that Jesus’ arrest and execution had happened ‘around Passover’ without being more exact about the times. It is safe to say ‘some days before the Passover feast’. Then, over time, after the resurrection, believers metaphorically thought of Jesus as the ‘paschal lamb’, and so thought of the day of his death as the day of preparation for Passover (when paschal lambs were killed). A later development would have been the idea that we have a new Passover feast (in Jesus’ death and resurrection’) and it would be best kept up on the day of the old Passover feast. These spiritual thoughts are of course mutually contradictory. There are implications too for the timing and the meaning of the last supper (when? And is it a Passover meal?)