A Christmas Eve mass was held on Saturday by the Fener Greek Orthodox Patriarchate in Istanbul.
The celebrations began early Saturday with a mass held in Hagia Yorgi Church led by Patriarch Bartholomew.
Greek Deputy Foreign Minister Ioannis Amanatidis and Ambassador to Turkey Petros Mavroidis were also present during the service which was telecast live by Athens' official broadcaster ERT.
The service will be followed by ritual at the Fener dock in the Golden Horn, during which the patriarch will throw a large cross into the sea to be retrieved by a group of swimmers.
Due to a difference in calendars, many Orthodox churches mark Christmas Eve on Jan. 6 and Christmas is celebrated on Jan. 7 and not Dec. 25.
Several countries including Russia, Georgia, and Armenia celeberate Christmas in January.
The majority of Orthodox churches worldwide use the Julian calendar, created under the reign of Julius Caesar in 45 BC, and have not adopted the commonly used Gregorian calendar, proposed by Latin Pope Gregory of Rome in 1582.
The former calendar runs 13 days behind.
