The Early Christians
n“The Quartodecimans contentiously keep Passover on one day, once per year...They keep the Passover on whichever day the fourteenth of the month falls...Christ had to be slain on the fourteenth of the month in accordance with the law”

 - Epiphanius. The Panarion of Epiphanius of Salamis, Books II and III (Sects 47-80), De Fide. Section IV, Verses 1,3;1,6;2,6. Translated by Frank Williams. EJ Brill, New York, 1994, pp. 23-25).