Okay, maybe we're just using different terminology. Biblically Passover IS the preparation day for the first day of Unleavened Bread. Remember how the bible shows that the day of Passover, which begins on nisan 14 did not have a commandment to rest? That means it's not a sabbath. But it is a preparation day for the high sabbath of the first day of unleavened bread which follows.
The new testaments uses the terms "passover" and "days of unleavened bread" almost interchangably.:
Luk 22:1 Now the feast of unleavened bread drew nigh, which is called the Passover.
Even today Jews don't make much of a distinction between the two, but they are biblically separate.
So yes, in this verse:
Joh 19:14 And it was the preparation of the Passover, and about the sixth hour. And he said to the Jews, Behold your king!
"Passover" is what technically and biblically is the first day of unleavened bread, or Nisan 15:
Lev 23:6 and on the fifteenth day of the same month is the Feast of Unleavened Bread to Jehovah. You must eat unleavened bread seven days.
The preparation day for this IS the biblical passover day:
Lev 23:5 In the fourteenth [day] of the first month at even [is] the LORD'S passover.
Understand? The death of Jesus MUST occur on passover, Nisan 14, that the original passover was killed. Must.
At the same time that the original passover lamb was killed (the beginning of Nisan 14 at sunset), Jesus had the last supper and instituted the remembrance of his death by the symbols of bread and wine:
Okay?