John 18:28:
Then they took Jesus from Caiaphas to Pilate's headquarters. It was early in the morning. They themselves did not enter the headquarters, so as to avoid ritual defilement and to be able to eat the Passover.
"Eating the Passover" is what Jesus and his disciples had done the night before according to the Synoptics.
John 19:14
Now it was the day of Preparation for (lit. of) the Passover; and it was about noon. He said to the Jews, "Here is your King!"
V. 31ff:
Since it was the day of Preparation, the Jews did not want the bodies left on the cross during the sabbath, especially because that sabbath was a day of great solemnity (lit. this sabbath day was a great one). So they asked Pilate to have the legs of the crucified men broken and the bodies removed. Then the soldiers came and broke the legs of the first and of the other who had been crucified with him. But when they came to Jesus and saw that he was already dead, they did not break his legs. Instead, one of the soldiers pierced his side with a spear, and at once blood and water came out. (He who saw this has testified so that you also may believe. His testimony is true, and he knows that he tells the truth.) These things occurred so that the scripture might be fulfilled, "None of his bones shall be broken."Here's John's agenda becomes quite clear: Jesus is the Passover lamb (cf. 1:29, compare Exodus 12:46), whence the time of his death, just before the actual beginning of the festival, which started with the Passover meal. All of this builds on Mark's earlier version of Jesus' strangely quick death (15:44ff).