December 12 in Eastern Orthodox liturgical calendars is a feast day and a day of commemoration of saints and martyrs. Although some Orthodox churches use the Revised Julian Calendar and others use the traditional Julian calendar, the fixed commemorations for their respective December 12 are broadly the same, no matter which calendar is used.
Hieromartyr Alexander, Archbishop of Jerusalem (250-251)
Martyr Aitherius (Aetherius), under Maximian, tortured and beheaded for refusing to sacrifice to idols (c. 286-305)
Saint Spyridon the Wonderworker, Bishop of Tremithus (348)
Venerable Amonathus, Monk of Pelusium.
Venerable Anthus, Monk of Palestine.
Martyr John, Abbot of the Zedazeni Monastery, Georgia (9th century) (see also: May 7)
Martyr Synesius (Synetus) of Rome, a Reader, tortured and beheaded for refusing to sacrifice to idols (270-275)
Martyrs Maxentius, Constantius, Crescentius, Justinus and their Companions, martyrs in Trier in Germany in the reign of Diocletian, under the governor Rictiovarus (c. 287)
Saint Abra of Poitiers, daughter of Saint Hilary of Poitiers in France (c. 360)
Saint Corentin (Corentinus), first Bishop of Quimper in Brittany, he had lived as a hermit at Plomodiern (490)
Saint Finian of Clonard and Skellig Michael, teacher of Ireland and one of the fathers of Irish monasticism (549)
Saint Columba of Terryglass (Columba of Tyrdaglas), born in Leinster in Ireland, he was a disciple of Saint Finian and Abbot of Tyrdaglas in Munster (552) (see also: December 13)
Saint Gregory of Terracina, a disciple of Saint Benedict, and with his brother Saint Speciosus, a monk at Terracina in Italy (c. 570)
Saint Cormac (Cormac mac Eogain), an Abbot in Ireland and friend of Saint Columba (6th century)
Saint Colman of Glendalough in Ireland, Abbot (659)
Saint Agatha, nun at Wimborne in Dorset in England and a disciple of Saint Lioba, she went to Germany to help Saint Boniface in his missionary work (c. 790)
Saint John, Metropolitan of Zichnon (Zichne), founder of the Monastery of the Forerunner on Mt. Menikion (north-east of Serres) (1333)