The Revised Julian Calendar for the Fixed Feasts

In May 1923 a pan-Orthodox congress meeting in Constantinople took up a proposal to bring the fixed feasts back into alignment with the seasons without simply adopting the Gregorian calendar wholesale. The congress's astronomical delegate, the Serbian scientist Milutin Milankovic, proposed a new leap year rule: a year divisible by four is a leap year, except that a year divisible by one hundred is not, unless dividing it by nine hundred leaves a remainder of two hundred or six hundred, in which case it is a leap year after all. That rule tracks the true solar year even more closely than the Gregorian reform of 1582, and the two calendars will not diverge by even a single day until the year 2800. On the ground the change was simple: 1 October under the old Julian reckoning became 14 October, dropping thirteen days at a stroke. What the congress adopted was narrower than a full modernisation. It moved only the fixed feasts onto the new reckoning; the moveable cycle governing the date of Pascha stayed on the unrevised Julian computation, so churches that took up the reform kept a different Christmas from their Old Calendarist neighbours while continuing to celebrate Easter on exactly the same day as they always had.

Adoption split the Orthodox world rather than uniting it. The Ecumenical Patriarchate of Constantinople, the Church of Greece, the Church of Cyprus, the Patriarchates of Alexandria and Antioch, and later the Romanian Orthodox Church, took up the revised reckoning for their fixed feasts. The Patriarchates of Jerusalem and Russia, along with Serbia, Georgia and Mount Athos, kept the unrevised Julian calendar entire, so the Nativity itself now falls on two different calendar dates depending on which jurisdiction a believer belongs to. Inside the churches that did adopt the change, a further division opened. Communities that considered the reform an unauthorised departure from received practice, and in some readings an opening toward union with Rome, broke communion with their own hierarchies and organised themselves as Old Calendarist bodies, later gaining their own bishops and, in places, their own parallel church structures; the movement in Romania is a documented case of a church born directly out of state pressure to conform to the new reckoning. Because the Paschal cycle was left untouched by the 1923 reform, the split is visible only in the fixed calendar of saints and feasts. Old and New Calendarists keep the same Pascha every year, which is why the disagreement reads as a dispute over dates rather than a doctrinal rupture.