Synaxis of the Three Hierarchs: Basil the Great, Gregory the Theologian and John Chrysostom: During the eleventh century, disputes raged in Constantinople about which of the three hierarchs was the greatest. Some preferred Saint Basil (January 1), others honored Saint Gregory the Theologian (January 25), while a third group exalted Saint John Chrysostom (November 13).
Dissension among Christians increased. Some called themselves Basilians, others referred to themselves as Gregorians, and others as Johnites.
By the will of God, the three hierarchs appeared to Saint John the Bishop of Euchaita (June 14) in the year 1084, and said that they were equal before God. “There are no divisions among us, and no opposition to one another.”
They ordered that the disputes should stop, and that their common commemoration should be celebrated on a single day. Bishop John chose January 30 for their joint Feast, thus ending the controversy and restoring peace.
— Text from oca.org (Link opens in a new tab)