Darrell Bock addresses a difficult scriptural questions. Here is his conclusion:
So where does this leave us? Two approaches could work. The early sacrifice might explain what is taking place or reading John’s Preparation as referring to the Sabbath preparation in the shadow of the Passover. If the latter is the point, then John is saying that Jesus is crucified in the mix of the Passover season, not on the day of Passover. This can work in the sense that the entire period is associated with the Passover. A modern analogy would be that people celebrate Christmas office parties all the time and it is not Christmas. Such associations are popular in orientation and not technical. So Jesus is crucified in the midst of the Passover season with his death connected to a Passover meal and so he is seen as crucified with a Passover significance. It may be that rather than trying to work out all the details of how this works technically, we are better off to see the season being appealed to in a popular ancient manner and the association made that way. The point should give us pause in not over-literalizing as we read some of these texts. So one or a combination of the solutions noted above could well be answers to the charge of a clear error but being able to show it is more difficult. If less technical approach is taken then we are dealing with a popular reckoning in a generalized ancient chronological approach as a key to understanding what is taking place. Also what we have in not an error but the application of a season that ran many days to events tied to Jesus’ death. All of this is quite plausible given the significance of this season in the Jewish calendar and its shadow on the Jesus event.