Yeshua and his disciples were Galileans. They naturally observed the Galilean festival traditions (it would have been unthinkable for them to do otherwise). The Judeans were somewhat understanding about the distances that had to be traveled by the Galileans and so allowed for their slightly different traditions to accommodate this difficulty; but they didn’t care for a couple of other additions that BOTH the Galileans and the Samaritans made to the Passover rituals that had little to do with travel distances and times: they added in an extra ritual celebration that the Judeans did not recognize. The celebration was called seudah maphsehket and it happened as the day was changing from Aviv 13 to Aviv 14. Remember, now, Passover was on Aviv 14. Also remember that the day changes at about 7 pm in the evening time.
In this celebration the Galileans and the Samaritans put an emphasis on the firstborn aspect of the Exodus, calling to mind that it was the firstborn Israelites who were protected from death and the firstborn Egyptians who were killed. So the Galileans declared that Aviv 14, the day of Passover, was to be a day of fasting for firstborn sons of each family in honor of the Lord saving their lives. However, they also added in a ritual meal that occurred at the beginning of Passover (Aviv 14th) called seudah maphsehket. Since the Hebrew day changes at sundown, the first meal of a new day for any Israelite would be dinner...their nighttime meal, right? For a Westerner, our first meal of the day is breakfast, because it occurs at around sunrise, which is the beginning of our day. So the firstborn sons of the Galileans (and the Samaritans) would have a meal to begin the day of Passover (a dinner meal), and then fast for the next 24 hours until it was time for the official Passover Seder (meal).
This is not conjecture or some new modern interpretation. This is to be found in the ancient Hebrew Mishnah fully recognized by religious Jews. By the way, this added celebration of having a dinner meal to start out the day of Passover that is called seudah maphsehket literally translates to...the last supper! The last supper title for them meant that this would be the last supper for a firstborn Hebrew who lived in either the Galilee or Samaria (they would fast) until he celebrated the Passover meal along with all other Hebrews. I hope some mental light bulbs are starting to go off.
It has long been recognized that in antiquity there were two Passover Seders; one the night before Passover and other the night of Passover. It’s the one that occurs on the night of Passover that Jews today celebrate, and that Christians are pretty much aware of. However since the details have been buried deep in the bowels of Jewish historical documents the realities of this dual seder, and how the two meals differed, and who participated in them, and why, and what was served has been overlooked.
There are a couple of reasons that we are carefully going over the laws concerning these Biblical feasts; first, because the way that some Jews and Christians celebrate those holy days today is not necessarily Scripturally accurate and second is because this was the series of festivals during which Yeshua HaMashiach celebrated a final meal with His disciples, was betrayed and arrested, tried and executed, and was buried and arose from the dead. This was the climax of what Yeshua had come for in the first place and it will remain the most important part of His earthly ministry until He comes again for the next stage in God’s redemption process.