In relation to the day on which Jesus was crucified, on what day does John say that the religious leaders partook of the Passover? See Joh 18:28, 19:14,31,42; cf. Mat 27:62, Mar 15:42, and Luk 23:54, and notice that the preparation day was for the Sabbath rest required by the Passover and the first day of Unleavened Bread that was beginning Thursday evening, not the seventh day Sabbath that would begin Friday evening. In relation to the day on which He was crucified, on what day do the Synoptic gospels say that Jesus and His disciples partook of the Passover? See Mat 26:17-20, Mar 14:12,16-18,26-27,32,43,53, Mar 15:1,15,22, etc…, Luk 22:7-8,14-15. How is it possible that the Passover could be reckoned to occur on two different days? Recall that the Jews used a lunar calendar, and reckoning the 14th day of Nissan on which the Passover occurred required sighting the new moon, which from different locations could happen on different days, as is the case with the Muslim holiday of Ramadan even today. Note: the exact time of the conjunction of the moon with the earth and the sun that marks the new moon varies with each new moon; in many months it is clearly on one day or another, but in certain months, especially when determined visually, it is ambiguous. I.e., in some months it may occur very close to midnight according to our Roman reckoning of the start of a new day, or very close to sunset according to the Jewish reckoning. Whereas the official reckoning of the Jewish leaders in Jerusalem placed Nissan 14 on Thursday, others reckoned it as starting a day earlier. Considering also the logistics of servicing the large number of people in Jerusalem gathered for the feast, it is not inconceivable that those who glimpsed the new moon a day earlier would be accommodated with Passover lambs from the temple on Wednesday; cf. again Mar 14:12.
As their Rabbi, and because Jesus celebrated the Passover on Wednesday evening in order to institute the Lord’s Supper, on what day would His disciples and the early church have naturally assumed was the “correct” day to observe the Passover, and that is reflected in the Synoptic accounts that were written first? How does this help us to understand why it was only later through John’s gospel that the Church came to understand the significance that the Jewish leaders reckoned that the Passover began a day later, so that according to their reckoning they had Jesus put to death at the very time they were also sacrificing their Passover lambs? What does this again teach us about the magnificence of God’s ways to effect salvation for those who seek Him while at the same time preparing for destruction those vessels of wrath who obstinately refuse His grace? For consider the potential impact Jesus’ death at exactly the same time that their Passover lambs were being sacrificed would have had upon the heart of each individual Jewish leader: How could it not either so completely harden their hearts as to separate them unto perdition for clinging to the nature of the kingdoms of this world that sacrifices others for one’s own worldly good, or so prick their conscience as to recognize God’s hand at work in the symphony of such events as to lead them to repentance? Cf. Act 6:7.
Significantly, in the careful chronological account of events that Scripture describes as having happened on Friday, Saturday, Sunday, Monday, and Tuesday, what is the very next event recorded that according to this understanding would indeed have happened on Wednesday? See Mat 26:17, Mar 14:12, and Luk 22:1-7 with their previous contexts; cf. also Joh 13:1ff for the upper room discourse that includes much greater detail about the Last Supper, and note that John is completely silent about the meal that Jesus ate with the disciples being the Passover, emphasizing instead the official Passover celebrated by the religious leaders on Thursday that had Jesus dying at exactly the same time as the Passover lambs which prefigured Him.
Notice also that for those celebrating the Passover on Wednesday evening, Wednesday would have been a preparation day, and Thursday (the day on which Jesus was crucified) a required Sabbath, followed by a Sabbath rest on Friday imposed by the religious leaders in Jerusalem who celebrated the Passover starting Thursday evening, and then the seventh day Sabbath starting Friday evening through Saturday. What do these sovereignly ordained days of rest for Christ’s followers during the events of His death and aftermath teach us that He would have us do in such circumstances that are completely out of our control? Cf. Exo 14:13-14.