Greek Old Calendarists

Greek Old Calendarists (Greek: Παλαιοημερολογίτες, Paleoimerologites), sometimes abbreviated as G.O.C., are groups of Old Calendarist Orthodox Christians that remained committed to the traditional Orthodox practice and are not in communion with many other Orthodox Churches such as the Orthodox Church of Greece, the Patriarchate of Constantinople, or the Church of Cyprus. The split began with a disagreement over the abandonment of the traditional Church Calendar (also called the Julian Calendar) in preference to the adoption of the Papal Gregorian Calendar and over other liturgical reforms that were introduced.

Until 1923 the Eastern Orthodox Church universally used the Julian Calendar, whereas the Roman Catholic Church, under Pope Gregory XIII, conducted a calendar reform and adopted the modern Gregorian calendar in 1582. The difference between the two calendars is 13 days between 1900 and 2100.

For civil and governmental uses, the Julian Calendar remained the official calendar in most Orthodox Christian nations until the early 20th century. The Gregorian calendar was adopted for civil uses by Bulgaria in 1916, the Ottoman Empire in 1917, Soviet Russia in 1918, Romania and Yugoslavia in 1919. Greece officially adopted the Gregorian calendar on 16 February 1923, which became 1 March, and was the last major country to do so.

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