The Jewish calendar is lunar and the xtian calendar is solar. Passover is for 7 days in Israel and 8 days outside of Israel.
Was Jesus' Last Supper a Passover Seder?
Dr. Michael J. Cook
Ask virtually anyone: "Was Jesus' Last Supper a Passover seder?" and the response is likely to be "Of course!"seder plate 2
Yet, Jesus could not have known what a "seder" was, let alone have modeled his Last Supper after one. The elements of even the primitive seder originated decades after he died.
The Gospels date Jesus' ministry to the period of Pontius Pilate, Roman prefect of Judea from 26 C.E. to early 37 C.E. Jesus' year of death is unknown; scholars settle on between 30 and 33 C.E.
At that time, the core element of Passover observance had been Jerusalem's sacrificial cult, from 621 B.C.E. (when the biblical mandate first appeared) up until 70 C.E. (the destruction of the Second Temple). Jewish families brought paschal (Passover) lambs for sacrifice on the Temple altar as biblically prescribed: "Thou shalt sacrifice the Passover offering...in the place which the Lord shall...cause His name to dwell [Jerusalem's Temple]" (Deuteronomy 16:2, 5-6); and the practice of King Josiah: "In the eighteenth year of King Josiah [621 B.C.E.] was this Passover kept...in Jerusalem" (Second Kings 23:21-23). For the ceremony, the kohanim (priests) conducted the sacrificial rite. Then families retrieved and consumed their meat as the main part of their Passover meal, which also included unleavened bread and bitter herbs (recalling the Hebrews' enslavement in Egypt). Passover meals Jesus experienced in his lifetime would have had to be along these Temple-centered lines.
Then, in 70 C.E., approximately 40 years after Jesus' death, Rome destroyed the Second Jerusalem Temple, thus ending the required central component of Passover observance, as sacrifice of paschal lambs by the Temple priests was no longer possible. Instead, the early rabbis eventually introduced an inchoate, rudimentary practice that over the ensuing decades evolved into a new way of observing Passover. Thi s would become known as a "seder," Hebrew for "order," because the ceremony followed a set sequence of liturgical recitations and ritual foods narrating the Passover saga, ultimately to be governed by an instructional guide called the haggadah. In our oldest reference, the early third century rabbinic compendium, the Mishnah, we read that Gamaliel II, the greatest rabbi of the post-destruction era (likely during the late 80s C.E.), customarily said: "Whoever does not mention [expatiate upon] these three things on Passover does not discharge one's duty...: the Passover offering [lamb], unleavened bread, and bitter herbs" (Pesahim 10:5). Thus the core Temple-centered observance mutated from sacrificing lambs into drawing upon Passover motifs to retell the Hebrews' escape from Egypt.
Centuries of further embellishment and refinement produced the full-fledged, mature seders we know today-the kind that many modern churches adopt and adapt in "reenacting" the Last Supper even though no such seder could have been practiced during Jesus' day.