Let the people of Israel keep the Passover at its appointed time.
Numbers 9:2

God sets the time for his holy days, not the Pope, not the rabbis, not you. That doesn't mean we should disregard what the rabbis and theologians say about how the Moedim are to be celebrated--there's usually a good reason for their opinions--but they don't have the final say, and, in the end, you have to follow the Scriptures and your conscience.