1923 — The Pan-Orthodox Congress and Milanković's Rule
Congress of Constantinople, May-June 1923
A meeting convened by the Ecumenical Patriarchate produced the Revised Julian calendar — astronomically more accurate than the Gregorian, aligned with it for centuries to come, and adopted only in part.
The proposal
The Serbian astronomer and geophysicist Milutin Milanković proposed a leap rule in which century years are leap years only when division by 900 leaves a remainder of 200 or 600. That gives a mean year of 365.242222 days — closer to the tropical year than the Gregorian 365.2425.
Alignment with the Gregorian
The two rules produce identical dates from 1600 until 2800, when they first diverge. So a Revised Julian church and a Gregorian church keep fixed feasts on the same civil day today, despite following different rules — a point frequently confused with the claim that the Orthodox 'adopted the Gregorian calendar'. They did not adopt it; they adopted a different rule that currently agrees with it.
Pascha was deliberately left alone
The Congress did not move the Paschal computation onto the new solar rule in practice. Orthodox Pascha continued — and continues — to be computed on the traditional Julian-based framework. This is the single most important thing to understand about the 1923 settlement.
The reception was divided
The Congress itself was contested: several churches did not participate or did not regard it as binding, and it was not an ecumenical council. Adoption followed church by church over subsequent years, and some churches never adopted it at all.
The cost
Adoption produced lasting division. Old-calendarist bodies broke communion with their mother churches over the change, most visibly in Greece from 1924 onward. Whatever one's judgement of the reform, the schisms are part of its documented result.
Citations on this file
Sources
- Ecumenical Patriarchate of ConstantinopleConvenor of the 1923 Congress; primary see for its acts.https://ec-patr.org/ ↗
- U.S. Naval Observatory — calendar referenceRevised Julian leap rule and mean year length for comparison with the Gregorian.https://aa.usno.navy.mil/faq/calendars ↗
Links are pointers for further reading. The claim is what is sourced, not the website.