St. Symeon, Archbishop of Thessaloniki, liturgist and theologian.
St. Symeon was a monk of Constantinople who became Archbishop of Thessaloniki in the early fifteenth century, the last Orthodox hierarch of the city before its fall to the Ottomans. He is remembered above all for his writings on the Divine Liturgy and the sacraments, which remain a chief source for the understanding of Orthodox worship, and for his pastoral care of a besieged city.
He reposed in 1429 and is commemorated on September 15.
Feast day
On the New Calendar, Symeon of Thessaloniki is commemorated on September 15. Churches on the Old (Julian) Calendar keep the feast on September 28 of the civil calendar.
Also commemorated on September 15

Philotheos the Presbyter
Venerable, Φιλόθεος
Venerable Philotheos the Presbyter and Wonderworker of Bithynia.
Name days: Philotheos, Filotheos, Philotheus
Bessarion of Larissa
Hierarch, Βησσαρίων Λαρίσης
St. Bessarion, Archbishop of Larissa, founder of the Dousikou Monastery.
Name days: Vissarion, Bessarion, Vissarionas
John the New Martyr of Crete
Martyr, Ιωάννης ο Κρης
New Martyr John of Crete, martyred at New Ephesus under the Ottomans.
Porphyrios the Mime
Martyr, Πορφύριος ο Μίμος
Holy Martyr Porphyrios the actor, baptized on stage and martyred for Christ.
Joseph the New of Partos
Hierarch, Ιωσήφ ο Νέος
St. Joseph the New of Partos, Metropolitan of Timisoara.