Their story
Basil the Great, Gregory the Theologian and John Chrysostom were bishops and writers of the 300s, and Basil and Gregory, who is also called Gregory of Nazianzus, had studied together at Athens. In Constantinople in the 1000s, people argued over which of the three was the greatest. The service books tell that the three appeared to John, bishop of Euchaita, said that they were equal before God and asked for one feast for them all, and so they have shared a single day ever since.
Synaxis of the Ecumenical Teachers and Hierarchs, 30 January, Orthodox Church in America
Their feast day
30 January: Their shared feast in the Orthodox churches on the new calendar. Those on the old calendar keep it on 12 February.
Synaxis of the Ecumenical Teachers and Hierarchs, 30 January, Orthodox Church in America
Why people ask The Three Holy Hierarchs
Students and exams
In Greece they are the patrons of learning and education. The University of Athens declared them so in 1841, and Greek schools kept their feast as a holiday until 2020.
“The Three Hierarchs: everything you need to know about 30 January”, To Vima
Where it comes from
Who wrote it
Greek schools and churches sing this hymn on their feast. No one knows who wrote it.
Ὡρολόγιον τὸ Μέγα (Venice, 1838), p. 288, the note on the feast
In Greek
Τοὺς τρεῖς μεγίστους φωστῆρας, τῆς τρισηλίου Θεότητος,τοὺς τὴν οἰκουμένην ἀκτῖσι, δογμάτων θείων πυρσεύσαντας·τοὺς μελιρρύτους ποταμοὺς τῆς σοφίας,τοὺς τὴν κτίσιν πᾶσαν θεογνωσίας νάμασι καταρδεύσαντας·Βασίλειον τὸν μέγαν, καὶ τὸν Θεολόγον Γρηγόριον,σὺν τῷ κλεινῷ Ἰωάννῃ, τῷ τὴν γλῶτταν χρυσορρήμονι·πάντες οἱ τῶν λόγων αὐτῶν ἐρασταί, συνελθόντες ὕμνοις τιμήσωμεν·αὐτοὶ γὰρ τῇ Τριάδι, ὑπὲρ ἡμῶν ἀεὶ πρεσβεύουσιν.
