13 Now before the Feast of the Passover, when Jesus knew that his hour had come to depart out of this world to the Father, having loved his own who were in the world, he loved them to the end. 2 During supper… (Jn 13:1-2).
28 Then they led Jesus from the house of Caiaphas to the governor's headquarters. It was early morning. They themselves did not enter the governor's headquarters, so that they would not be defiled, but could eat the Passover (Jn 18:28).
14 Now it was the day of Preparation of the Passover. It was about the sixth hour. He said to the Jews, “Behold your King!” (Jn 19:14).
Some scholars think there's a discrepancy between John's Passion week chronology and the Synoptic chronology. There are different proposals for finessing this alleged discrepancy.
1) One issue concerns the timing of the Crucifixion. Did it take place at the third hour (Mk 15:25) or the sixth hour (Jn 19:14)?
i) One proposal is that John uses the Roman system whereas the Synoptics use the Jewish system (e.g. Andrew Steinmann). But that's disputed.
ii) Perhaps a better explanation is that, before the advent of clocks, when people told time by the sun, the time of day was inherently imprecise. Sunrise and sunset vary throughout the year. Hence, it's anachronistic for modern readers, with digital clocks, to expect precise hourly time-divisions.
2) A more substantial issue concerns the relationship of the Last Supper and the Crucifixion to the Sabbath.
i) One suggestion is that John and the Synoptics are working from different, independent traditions (e.g. J. R. Michaels). The problem with that suggestion is that if John and the Synoptics endorse divergent traditions, then that's at odds with the inerrancy of Scripture.
ii) There's also the question of whether John was familiar with the Synoptic Gospels. Assuming that's the case, then even if, for whatever reason, his chronology is different, that wouldn't be a mistake on his part. Rather, that would be intentional. It's not as if his chronology is different because he was ignorant of Synoptic chronology. Rather, the difference is deliberate.
iii) Apropos (ii), another suggestion is that John adapted the timeline for symbolic reasons, to synchronize the Crucifixion with Jewish pilgrims sacrificing their paschal lambs (e.g. Leon Morris, Craig Keener). However, that's subject to certain objections.
a) This is based on later Jewish tradition, which may not go back to the time in question.
b) Even if the tradition is accurate, it might be too subtle for John's audience. That, however, assumes John wrote with just one audience in mind. But authors often pitch their work at different levels. The basic story is comprehensible to the average reader. But they also write with the ideal reader in mind–someone who will appreciate the subtleties.
c) If John changed the day to make a theological point, there's no underlying event to support the symbolism.
iv) Perhaps the best suggestion is that John is referring to something else. As one scholar explains:
If one is not content to posit a contradiction between John and the Synoptists (a position which has its own difficulties, not the least of them being the indications that John himself knows, and sometimes follows, the Synoptic chronology [See below, pp293-294]), various possible ways of reconciling them are worthy of consideration.
"The Preparation of the Passover" (Jn 19:14) is a phrase which naturally recalls the rabbinical expression "the Eve of the Passover," meaning Nisan 14, "The Passover" itself being Nisan 15. However, the rabbinical form of language is curiously at variance with the OT, where it is Nisan 14 that is "the Passover," and Nisan 15 is the first day of "Unleavened Bread" (Lev 23:5f; Num 28:16f); and there is no clear example of the rabbinical phraseology in the NT. So, as the "Preparation," paraskeue, commonly means Friday (the preparation for the Sabbath), and as the word is used twice in this sense in the very same chapter of John (Jn 19:31,42), it seems better to understand "the Preparation of the Passover" as meaning "the Friday of Passover week"–either the Friday of the Jewish week (from Sunday to Saturday) within which Passover fell that year, or, perhaps better, the Friday within the feast of Passover and Unleavened Bread, though of as a single festival (cp. Mk 14:1; Lk 22:1).
"Eat the Passover" (Jn 18:28) is more difficult, for there is no doubt that it would usually mean "eat the Passover lamb." But since it turns out, in light of the foregoing evidence, that this interpretation would make John contradict himself about the chronology, a less usual interpretation becomes a distinct possibility. The sacrifice of the Passover lamb, and the meal which followed, were only the first (though the most important) of the many sacrifices and sacred meals which took place throughout the Passover and Unleavened Bread, and had done so since OT times. In the first century, it was held that the command not "to appear empty" before the Lord at the pilgrim feasts (Exod 23:15; 34:20; Deut 16:16) had a precise meaning: it meant each male Israelite bringing a burnt offering and a peace offering, in addition to the Passover lamb; and this obligation is the subject of the tractate Hagigah in the Mishnah. Those referred to in Jn 18:28 as wanting to remain ceremonially clean so as to "eat the Passover" are the chief priests and the Pharisees (cp. v3). The Pharisees would have been very scrupulous about the Hagigah duty, and as it involved a peace offering, which necessarily included a sacred meal, they would certainly have wanted to remain ceremonially clean so as to be able to eat it. Even more would this have concerned the chief priests, since a share of every peace offering went to the priest who offered it. Moreover, the peace offering might be an ox from the herd, rather than a lamb or goat from the flock.
The question, therefore, faces us, was it possible to use phrases like "to sacrifice the Passover" and "to eat the Passover" to cover these other sacrifices and sacred meals as well? In OT times, Deut 16:2f shows that it was, and as the OT was the Bible of Judaism, and the Pentateuch was reckoned its most important part, it was always possible for Pentateuchal phraseology to be echoed or copied. What Deut 16:2f says is:Though shalt sacrifice the Passover unto the Lord thy God, of the flock and the herd, in the place which the Lord shall choose to cause his name to dwell there. Thou shalt eat no leavened bread with it (i.e. with the Passover); seven days shalt thou eat unleavened bread with it, even the bread of affliction.Here the phrase "sacrifice the Passover" is actually used, and the phrase "eat unleavened bread with the Passover" (and therefore "eat the Passover" itself) is clearly implied; and in both cases the reference is to what goes on for seven days, and includes the sacrificing and eating of oxen from the herd as well as lambs and kids from the flock. The usage is found again in the Hebrew of 2 Chron 30:22, in the account of Hezekiah's Passover, where the literal meaning isSo they ate the festal sacrifice (i.e. the Passover, v18) for the seven days, offering sacrifices of peace offerings, and giving thanks to the Lord, the God of their fathers.Moreover, the earliest example occurs in biblical Greek as well, since Deut 16:2f is literally translated in the Septuagint (whereas 2 Chron 30:22 is paraphrased). R. Beckwith, Calendar and Chronology, Jewish and Christian (E. J. Brill 1996), 290,294-296. Cf. Steinmann, From Abraham to Paul (Concordia 2011), 276ff.