Aka the Quartodecimans, the fourteenthers.
Victor [died 199 A. D.], who presided over the church at Rome, immediately attempted to cut off from the common unity the parishes of all Asia, with the churches that agreed with them, as heterodox; and he wrote letters and declared all the brethren there wholly excommunicate.
-- Eusebius, Ecclesiastical History, V.XXIV.9.
Orthodox Easter 2024 is Sunday, May 5th, five weeks after Easter in the West:
Orthodox Pascha often occurs later in the spring ... especially out of sync with the actual astronomical phenomena linked to an accurate calculation of the Paschal date. ... During the 21st century, the Orthodox and Western Churches will share a common celebration of Pascha only 31 times.
