It was during Passover that Yahweh brought the children of Israel out of Egyptian bondage. Today Passover, Unleavened Bread, Firstfruits and sometimes even Pentecost, are all referred to as Passover. The reason for this could be because all of these are seen as “The Season of Our Liberation”, in its entirety. Truth is, Passover only lasted for one day. After that it became the Feast of Unleavened Bread.
Passover is celebrated on the 14th day of the first month (Aviv). Aviv means ripening. As with the other Feasts, there is an agricultural element. The barley became ripe during this month. If the barley was not ripe enough when a new moon was seen so that an omer (about 2 quarts) of barley could be harvested by Firstfruits, then they waited until the next month to proclaim aviv.
On the tenth of the first month a spotless lamb was chosen for each family. This lamb was brought into the house and diligently loved and cared for until the 14th day of the month. On that day the lamb was killed and prepared so that it could be eaten for the Passover meal. The meal itself would not be eaten until the sun set on the 14th, at which point the 15th of the month would have begun. Remember, on Yahweh's calendar, a day goes from sunset to sunset. So, actually Passover was just a preparation day for the Feast of Unleavened Bread. Passover was just the day that the lamb was killed and prepared.
In the New Testament we have many scriptures that speak of “the preparation day” (Matthew 27:62, Mark 15:42, Luke 23:54, John 19:31, 42). This is speaking of the 14th day of the first month when the lamb was killed and prepared (Passover). Passover (14th day of the month) was not a Sabbath. A person could buy and sell on this day. However, when the sun set and Unleavened Bread began (15th of the month) then it was a High Sabbath Day. No work could be done on this day. This is why they were hurrying to get Yeshua into the grave before the sun set.
By the time of the second temple, and before, a paschal lamb was also sacrificed for the nation as a whole. This would have been going on in the temple during the time of Yeshua's crucifixion.
Yeshua, as our Passover Lamb, was crucified on the 14th day of the first month (Passover) and He died on the cross at exactly the same time that the priest would have been sacrificing the lamb for the nation in the temple. This would have been at the 9th hour of the day (3 pm). This is when Yeshua would have proclaimed “it is finished” and then died. His body would then have been taken off of the cross and quickly lay in the tomb at the closing of the day (sunset). He would have been placed in the tomb just as The Feast of Unleavened Bread was beginning.