Quartodeciman

Etymology
From the, from  for the fourteenth day of the first month of the Jewish calendar, which is Nisan.

Noun

 * 1) Any of a group of early Christians (especially in Asia Minor, Syria, and Jerusalem) who observed Pascha (Christian Passover or Easter) on Nisan 14 of the Hebrew calendar, the day Jesus was crucified according to the Gospel of John, and the day before the beginning of Jewish Passover (also called the Feast of Unleavened Bread, which began on Nisan 15.

Adjective

 * 1) Of or pertaining to these people.