When preaching to Jews it was not necessary to define an exact day since it was common knowledge that it was the 14 of Nisan in the Passover. When preaching to Gentiles it was not a necessary item for their salvation and could be learned later to increase their Joy. Throughout the Asia Minor gatherings of believers the Lord's Table was celebrated on Nisan 14, as attested by Polycarp, a student of John the Revelator.
An exact day is not essential for our Salvation, but to follow our Lord's Way it brings greater joy. Since Jesus attached His Remembrance to that of the Passover, Jewish Remembrance it is a natural for Jewish converts to place The Lord's Table at Passover. But we need not do this Remembrance only once each year. We can do it anytime believers gather, and especially whenever we gather in His name, for there is He int he midst of us.
Nor does it mean one is preaching "another Jesus" if they hold to a wrong specific day of crucifixion, which was the point being refuted.