I can see how it might seem odd, but it's actually very simple brother
Here is something to better explain this.
“Preparation.” At
John 19:14, the apostle John, in the midst of his description of the final part of Jesus’ trial before Pilate, says: “Now it was preparation of the passover; it was about the sixth hour [of the daytime, between 11:00 a.m. and noon].”
This, of course, was after the time of the Passover meal, which had been eaten the night before. Similar expressions are found at
verses 31 and
42. Here the Greek word pa·ra·skeu·e′ is translated “preparation.” This word seems to mark, not the day preceding Nisan 14, but the day preceding the weekly Sabbath, which, in this instance, was “a great one,” namely, not only a Sabbath by virtue of being Nisan 15, the first day of the actual Festival of Unfermented Cakes, but also a weekly Sabbath. This is understandable, since, as already stated, “Passover” was sometimes used to refer to the entire festival.—
Joh 19:31; see
PREPARATION.
Passover — Watchtower ONLINE LIBRARY