(7)Then came the day of Unleavened Bread on which the Passover lamb had to be sacrificed.
(8)Jesus sent Peter and John, saying, "Go and make preparations for us to eat the Passover."
From the info of verse 7, so when Jesus say "Go and make preparations for us to eat the Passover" I guess it happen in the time where the Jewish people either are preparing a lamb to be sacrificed (sacrificed in the same day) or even maybe some of the Jews are already sacrificing the lamb when Jesus say that.
Assuming my guessing is correct, the question is :
What date that event happen ?
13 Nissan ? 14 Nissan ? or 15 Nissan ?
The Catholic opinion is sought here.
The Reformed opinion is sought here