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History and general data

The characteristic of the old Julian calendar is that every fourth year is a leap-year. The Church adopted this calendar at the First Ecumenical Council in Nicea in the year 325. At the same time, a specific way of calculating was established to determine the dates when the Resurrection of Our Lord Jesus Christ (the Feast of Feasts) is celebrated. By canon, Easter falls on the first week after the first full moon after the spring Equinox. The ancient astronomers had two assumptions: first, that the Julian calendar is correct; second, that the Moon orbits the Earth once in exactly 28 days. Thus the history was divided into Great Indictions, each lasting 532 years, and in which the celebration of Easter is cyclically repeated. We are currently in the 15th Indiction that began in the year 1941. As we know today that both of the assumptions are incorrect, this manner of calculation rapidly lost its accuracy. Yet all Orthodox Churches still hold on to it.

The Julian calendar is late one day every 128 years in relation to the real astronomic time. Therefore, since the contrast between the real Equinox and the one that could have been expected by the calendar became apparent and visible, Pope Gregory XIII decided to introduce the Gregorian calendar (that was named by him). This calendar is today the regular civic calendar throughout the world and is used by the Roman Catholic Church, Old Catholic Church and all the Protestant Christian Churches. In the Gregorian calendar as well, every fourth year is a leap one, but this also goes for the secular years (ones divisible by 100), and thus years 1700, 1800 and 1900 were not leap, but year 2000 is. This calendar is much more precise and is late one day every 14.400 years compared to the real astronomic time. The difference between the Gregorian and Julian calendar at this moment equals 13 days.

Year 1917, Orthodox Churches decided to change the Julian calendar. The project was prepared by one of the greatest Serbian scientists, Milutin Milankovic (best known for providing a mathematical solution for the problem of the origin of Ice-ages which today stands as the rudiment of the currently valid theory given by the CLIMAP project). According to Milankovic’s calendar, every fourth year remains leap, but as for the secular ones, leap are only those that divided by 900 give the remainder of 200 or 600. Therefore, years 2000 and 2400 will be leap-years, but this calendar will differ from the Gregorian year 2800 when a day of difference will occur. Milankovic’s calendar is most accurate of all and is late one day just once every 48.000 years in relation to the real astronomic time.

Nevertheless, just three Churches decided on that Council to stick to the Julian calendar: Serbian, Russian and Jerusalem (as well as all the monasteries on the Holy Mountain). However, it was agreed that all Orthodox Churches celebrate Easter the old way, regardless of the time difference in celebrating the Fixed Feasts (the biggest being Christmas),.

This calendar

This is a first trial of an electronic format of the Orthodox calendar of the Serbian Orthodox Church. Our work gives as an output a table list of all the feasts for the given month and year by all the standards of the Patriarchate in Belgrade, hence taking care of the size of the feast and of the place of all the non-fixed feasts the Church celebrates.

Years can be tracked from 400 to even 300.000. Several remarks must be added here. Years in distant past, specially the ones before the XVI century are obtained fictively in the Gregorian calendar simply because it did not exist previously. Likewise, the further in past it is went, the more the names of the Saints lose sense because these people weren’t even born at the time. However, the descent into the past may benefit the historians and other people researching old documents because the events were often evidenced exclusively in relation to one of the non-fixed feasts.

As for the future, going too distant in the future also takes away some sense from using the calendar. Since every 100 years the difference between the Julian and Gregorian calendar increases a day (except when the year is divisible by 400), it is not difficult to calculate that Christmas as marked by the Julian calendar will slowly keep moving through all the seasons, and that would potentially generate a big confusion in people’s customs linked to certain feasts. Likewise, if the year 300.000 is looked at, it can be noted that the difference between the calendars will mount up to over 3 years (!). Nevertheless, in this fictious time, both calendars will be late several years in comparison to the real astronomic time, so all the Churches will certainly have to do something about it up until then :).

Nikola Lecic