Here is the biblical answer I've come up with since observant Christians get shy when they realize their favorite time of the year is as uninspired as the Bunny that lays eggs. is:
Passover never was changed in the bible, Every one in the Bible who wasn't pagan or heathen kept Passover according to the Law of YHWH God in Exodus 12... Jesus, Moses, the Apostles, the prophets, the king's of Israel, the Corinthians (1Cor 5, 10, 11) and so on. This thing called Easter Sunday or Paschal Sunday, or what ever you want to call it is a man made tradition of some sort. The Bible clearly Tells us of Christ's practice:
Joh 2:23 Now when he was in Jerusalem at the passover, in the feast day, many believed in his name, when they saw the miracles which he did.
Joh 12:1 Then Jesus six days before the passover...
Also it is interesting to note that the ordinance of the bread and wine in memorial if the death of Christ was tied to the Paschal meal and not to Resurrection of Christ as the nominal Sunday practice replicates:
Mat 26:19 And the disciples did as Jesus had appointed them; and they made ready the passover.
Luk 22:15 And he said unto them, With desire I have desired to eat this passover with you before I suffer: 16 For I say unto you, I will not any more eat thereof, until it be fulfilled in the kingdom of God. 17 And he took the cup, and gave thanks, and said, Take this, and divide it among yourselves: 18 For I say unto you, I will not drink of the fruit of the vine, until the kingdom of God shall come. 19 And he took bread, and gave thanks, and brake it, and gave unto them, saying, This is my body which is given for you: this do in remembrance of me. 20 Likewise also the cup after supper, saying, This cup is the new testament in my blood, which is shed for you.
The apostolic tradition of Paul: 1Cor 5:7 Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us: 8 Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth. 1Cor 11: 23 For I have received of the Lord that which also I delivered unto you, That the Lord Jesus the same night in which he was betrayed took bread: 24 And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me. note 25 After the same manner also he took the cup, when he had supped, saying, This cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me. 26 For as often as ye eat this bread, and drink this cup, ye do shew the Lord's death till he come.
It is obvious that from a Sola Scriptura (Scripture alone) and Tota Scriptura (all of scripture) standing this Easter business needs Reformed and purified.
The only discipes of Jesus who don't keep Passover are Christian's that would rather keep uninspired traditions that never entered in to the mind of God to communicate for his worship.