I am Jewish. We were discussing this same question on another thread about the slaughtering of the Lambs. I am getting ready to celebrate Passover, so I might be able to help.
Passover begins on Nisan 14. On that date, when we still slaughtered lambs at the Temple, the process began at the sundown of Nisan 14. Technically speaking, you could hold a Passover Seder then, if you were lucky to be one of the first to have your lamb slaughtered and bled and your dinner prepared.
But the slaughtering went on for a full day, “between the evenings” as Exodus 12.6 reads in Hebrew (it says “at twilight” in most English versions). That means between the sundown of Nisan 14 and Nisan 15 is all the time Jews (and the small number of priests by comparison) had to slaughter lambs for the nation enough for each family to have one in time for evening by Nisan 15.
Because you only had the time “between the evenings” to make preparation, someone was going to be the last to get their lamb ready. According to the law, you were to eat the lamb overnight and not leave any till morning. How could you do that if you could only slaughter lambs “between the evenings”?
Jews interpret this language in the law to mean that Nisan 14 has two evenings. Unlike other nights of the year, Passover has its own evening and the evening of Nisan 15. This is why today Jews observe Passover not on Nisan 14 but on Nisan 15, on the date when the last of the Jews in the past would have had their sacrifice ready.
But in the first century, Jesus could have been someone who had an early sacrifice. He could have had a Passover Seder on Nisan 14, a Thursday, and then been crucified on Friday. That evening would have also been Passover, the 15th of Nisan, another legitimate Seder night.
Of course I am sure people will challenge this, and I am Jewish. I am not a Messianic Jew or believe in Jesus as the Messiah (but I am part of the Catholic-Jewish dialogue and love the Catholics very much). This is just a theory and offers a possibility.