Easter is Not Passover
The first Christians being mostly Jews, continued to celebrate the Passover in remembrance of the death of Christ, the true Passover, and this was continued among those who from among the Gentiles had turned to Christ. Accordingly, the celebration was always on the Passover day - the fourteenth of the first month. Rome, however, and from her all the West, adopted the day of the sun as the day of this celebration. According to the Eastern custom, the celebration being on the fourteenth day of the month, would of course fall on different days of the week as the years revolved. The rule of Rome was that the celebration must always be on the Sunday - the Sunday nearest to the fourteenth day of the first month of the Jewish year. And if the fourteenth day of that month should itself be a Sunday, then the celebration was not to be held on that day, but upon the next Sunday. One reason for this was not only to be as like the heathen as possible, but to be as unlike the Jews as possible; this in order not only to facilitate the "conversion" of the heathen by conforming to their customs, but also by pandering to their spirit of contempt and hatred of the Jews. It was upon this point that the bishop of Rome made his first open attempt at absolutism.
- The Great Empires of Bible Prophecy, p. 383 by A.T. Jones (1898)