There are three Passovers in scripture:
1. Christ's Passover. On Passover evening He instituted the bread and wine of the New Covenant Passover memorial. On Passover day He offered Himself as a sacrifice, and Judgment was placed on Him instead of His people, initiating their deliverance.
2. Egyptian Passover. On Passover evening the memorial sacrificial meal was instituted by Moses and the blood was applied to the doors of Israelite homes in Egypt. Judgment went through Egypt but passed over God's people. Passover day Israel began leaving Egypt.
3. Abrahamic Passover. On the 14th of Abib at evening Abraham was given bread and wine by Melchizedek the priest of God and was blessed by him. That night God promised a covenant with Abraham. That day (Passover day) Abraham made a sacrifice and as the day ended God ratified the covenant with him and his descendants.
The Covenant with Abraham, the Exodus from Egypt, and the Crucifixion of Messiah all occurred on the exact same day centuries apart. Keeping Passover memorializes Christ and the New Covenant as the fulfillment of the ABRAHAMIC COVENANT, and not just the Passover in Egypt. It connects the believer with Abraham through Christ:
Luke 1:54,54-55 KJV
[54] He hath holpen his servant Israel, in remembrance of his mercy; [55] As he spake to our fathers,
to Abraham, and to his seed for ever.
Luke 1:68-75 KJV
Blessed be the Lord God of Israel; for he hath visited and redeemed his people, [69] And hath raised up an horn of salvation for us in the house of his servant David; [70] As he spake by the mouth of his holy prophets, which have been since the world began: [71] That we should be saved from our enemies, and from the hand of all that hate us; [72] To perform the mercy promised to our fathers, and to remember his holy covenant; [73]
The oath which he sware to our father Abraham, [74] That he would grant unto us, that we being delivered out of the hand of our enemies might serve him without fear, [75] In holiness and righteousness before him, all the days of our life.
John 8:56 KJV
Your father Abraham rejoiced to see my day: and he saw it, and was glad.
Galatians 3:7 KJV
Know ye therefore that they which are of faith, the same are the children of Abraham.
Galatians 3:14 KJV
That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith.
Concerning the DATE:
Galatians 3:15-17 KJV
Brethren, I speak after the manner of men; Though it be but a man's covenant, yet if it be confirmed, no man disannulleth, or addeth thereto. [16] Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ. [17] And this I say, that
the covenant, that was confirmed before of God in Christ, the law, which was four hundred and thirty years after, cannot disannul, that it should make the promise of none effect.
Exodus 12:40-42 KJV
Now the sojourning of the children of Israel, who dwelt in Egypt, was four hundred and thirty years. [41] And it came to pass
at the end of the four hundred and thirty years, even the selfsame day it came to pass, that all the hosts of the Lord went out from the land of Egypt. [42] It is a night to be much observed unto the Lord for bringing them out from the land of Egypt: this is that night of the Lord to be observed of all the children of Israel in their generations.
The Abrahamic Covenant was made 430 years prior the institution of the Sinaitic Covenant. Passover was 430 years TO THE DAY of the pilgrimage of Israel (as announced by God) in
Genesis 15.
Passover goes back to Abraham. And when we consider the word "seasons" in
Genesis 1 is the same word as Feasts and means "appointed times" it means the Divine Calendar was in place from the Beginning. Therefore, there is literally nothing "Jewish" about Passover. It is Christian, it is Abrahamic, it is Divine and stems from the Creation itself. Redemption was part of the Plan from the beginning!