See Dan 7:25 about such 'changes'.
But what did Paul say?
1Co 5:7 εκκαθαρατε ουν την παλαιαν ζυμην ινα ητε νεον φυραμα καθως εστε αζυμοι και γαρ το πασχα ημων υπερ ημων εθυθη χριστος
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: - 1 Cor 5:7
The Greek word is
πασχα, Pascha. Christ Jesus is our Pascha {notice it didn't say Jewish Pascha}, and is so being the sacrifice, which took place upon the 14th of Nisan/Aviv, Friday [6th day of the week] afternoon, around 3PM.
Again, the first day of the week, Christ is the Firstfruits, as Paul also stated in 1 Cor 15:20,23, after He arose from the dead.
This is what the Scripture says.
The earth also is defiled under the inhabitants thereof; because they have transgressed the laws, changed the ordinance, broken the everlasting covenant. Isaiah 24:5