Since the only instruction in the bible is to do this 'often', any date would not be wrong but doing it once a year is not often.
Memorial Date this year, why so far out ?
interestingly on one of the first passover after the death of the carpenter, there was no mention of a memorial service being held, still called a passover by christian writer, who of course wrote decades after the fact.
That's because they were written by fallible humans, nothing more.
And the fact that there was no Jesus, so it's all made up.