Revised Julian calendar


The Revised Julian calendar, less formally the new calendar, also known as the Milanković calendar, is a calendar proposed in 1923 by the Serbian scientist Milutin Milanković as a more accurate alternative to both the Julian and Gregorian calendars. At the time, the Julian calendar was still in use by all Eastern Orthodox Church and affiliated nations, while Catholic and Protestant nations were using the Gregorian calendar, which had been proclaimed by Pope Gregory XIII's papal bull Inter gravissimas in 1582. Milanković's aim was to discontinue the divergence between the naming of dates in Eastern and Western churches and nations and intended to replace the Julian calendar in Eastern Orthodox churches and nations. The Revised Julian calendar aligns its dates with the Gregorian calendar from 1 March 1600 through 28 February 2800.
The Revised Julian calendar has been adopted for ecclesiastical use by the Ecumenical Patriarchate of Constantinople, the Albanian Orthodox Church, the Greek Orthodox Patriarchate of Alexandria, the Greek Orthodox Patriarchate of Antioch, the Bulgarian Orthodox Church, the Romanian Orthodox Church, the Cypriot Orthodox Church, the Church of Greece, the Orthodox Church of the Czech Lands and Slovakia, the Orthodox Church of Ukraine, the Orthodox Church in America. It has not been adopted by the Russian Orthodox Church, the Serbian Orthodox Church, the Macedonian Orthodox Church, the Georgian Orthodox Church, the Polish Orthodox Church and the Greek Orthodox Patriarchate of Jerusalem. It has not been adopted by any nation as an official calendar. Instead, all of the Eastern Orthodox nations have adopted the Gregorian calendar as the official state calendar.
The Revised Julian calendar has the same months and month lengths as the Julian and Gregorian calendars, but, in the Revised Julian version, years evenly divisible by 100 are not leap years, except those years with remainders of 200 or 600 when divided by 900, e.g. 2000 and 2400 as in the Gregorian calendar.

Background

In the history of Christianity, divisions on which calendar to use were initiated after 1582, when the Catholic Church transitioned from the ancient Julian calendar to the new Gregorian calendar.
Eventually, by the 18th century, the Gregorian Calendar was officially adopted even in Protestant countries as the civil calendar, but still faced some opposition from smaller groups. In the Kingdom of Great Britain, the Gregorian calendar was officially introduced in 1752.
Around the same time, debates between those wanting to adopt the Gregorian Calendar and traditionalists wanting to keep the Julian calendar were also going on within several Eastern Catholic Churches. Those debates were focused mainly on ritual questions and ended in various compromises. The need for preservation of ritual differences, including various questions related to liturgical calendar, was consequently acknowledged by Rome.

Implementation


Century
year		Remain-
der on
divide
by 900		Is a
Revised
Julian
leap
year		Is a
Grego-
rian
leap
year		Revised
Julian is
same as
Grego-
rian
1000100
1100200
1200300
1300400
1400500
1500600
1600700
1700800
18000
1900100
2000200
2100300
2200400
2300500
2400600
2500700
2600800
27000
2800100
2900200
3000300
3100400
3200500
3300600
3400700
3500800
36000
3700100
3800200
3900300
4000400

Comparison of Revised Julian and Gregorian
calendar century years.

A committee composed of members of the Greek government and Greek Orthodox Church was set up to look into the question of calendar reform. It reported in January 1923. In the end, for civil purposes, the Gregorian calendar was adopted; the changeover went into effect on 16 February 1923/1 March 1923.
After the promulgation of the royal decree, the Ecumenical Patriarch, Patriarch Meletius IV of Constantinople, issued an encyclical on 3 February recommending the calendar's adoption by Orthodox churches, which is why it is sometimes also known as the Meletian Calendar. The matter came up for discussion at the Council of Constantinople, which deliberated in May and June. Subsequently, it was adopted by several of the autocephalous Orthodox churches. The synod was chaired by Meletius IV and representatives were present from the churches of Cyprus, Greece, Romania and Serbia. There were no representatives of the other members of the original Orthodox Pentarchy or from the largest Orthodox church, the Russian Orthodox Church.
The Serbian delegation presented a proposal by Maksim Trpković, which had a leap year rule in which century years would become common years, except those with remainders of 0 or 400 when divided by 900, which would remain leap years. However, it was rejected because the proposal would omit a leap year in 2000, which would cause it to differ from the Gregorian after only 77 years. Milanković proposed a small modification of Trpkovic's proposal, changing the timing of the century leap years to those with remainder 200 or 600 when divided by 900 in order to maximise the amount of time before it would differ from the Gregorian.
Milanković's arguments won the day. In its decision the conference noted that "the difference between the length of the political year of the new calendar and the Gregorian is so small that only after 877 years it is observed difference of dates." The same decision provided that the coming should be called, thus dropping thirteen days. It then adopted the leap year rule of Milanković. The proposed calendar was preferred over the Gregorian because its mean year was within two seconds of the then current length of the mean tropical year. The present vernal equinox year, however, is about 12 seconds longer, in terms of mean solar days.
The synod also proposed the adoption of an astronomical rule for Easter: Easter was to be the Sunday after the midnight-to-midnight day at the meridian of the Church of the Holy Sepulchre in Jerusalem during which the first full moon after the vernal equinox occurs. Although the instant of the full moon must occur after the instant of the vernal equinox, it may occur on the same day. If the full moon occurs on a Sunday, Easter is the following Sunday. Churches that adopted this calendar did so on varying dates. However, all Eastern Orthodox churches continue to use the Julian calendar to determine the date of Easter.
There were attempts to introduce Revised Julian as a religious calendar in the Soviet Union. On 12 June 1923, it was accepted by the short-lived schismatic Renovationist Church, which had seized church buildings with the support of the Soviet government while Patriarch Tikhon was under house arrest. After his release, on, he declared that all Renovationist decrees were without grace. On 15 October 1923, Patriarch Tikhon accepted the new calendar, but it caused disagreement among clergy, and 24 days later he reverted the decision. The present Russian Orthodox Church continues to use the Julian calendar for both its fixed festivals and for Easter.

Arithmetic

The following are Gregorian minus Revised Julian date differences, calculated for the beginning of January and March in each century year, which is where differences arise or disappear, until AD 10000. These are exact arithmetic calculations, not depending on any astronomy. A negative difference means that the proleptic Revised Julian calendar was behind the proleptic Gregorian calendar. The Revised Julian calendar is the same as the Gregorian calendar from 1 March 1600 to 28 February 2800, but the following day would be 1 March 2800 or 29 February 2800 ; this difference is denoted as '+1' in the table. 2900 is a leap year in Revised Julian, but not Gregorian: 29 February 2900 is the same as 28 February 2900 and the next day will be 1 March 2900 in both calendars - hence the '0' notation.
DatesRJ − GDatesRJ − GDatesRJ − G
Mar BC 1 – Feb AD 2000Mar AD 3600 – Feb AD 3800+1Mar AD 7200 – Feb AD 7400+2
Mar AD 200 – Feb AD 400−1Mar AD 3800 – Feb AD 40000Mar AD 7400 – Feb AD 7600+1
Mar AD 400 – Feb AD 6000Mar AD 4000 – Feb AD 4200+1Mar AD 7600 – Feb AD 7800+2
Mar AD 600 – Feb AD 800−1Mar AD 4200 – Feb AD 44000Mar AD 7800 – Feb AD 8000+1
Mar AD 800 – Feb AD 11000Mar AD 4400 – Feb AD 4700+1Mar AD 8000 – Feb AD 8300+2
Mar AD 1100 – Feb AD 1200−1Mar AD 4700 – Feb AD 48000Mar AD 8300 – Feb AD 8400+1
Mar AD 1200 – Feb AD 15000Mar AD 4800 – Feb AD 5100+1Mar AD 8400 – Feb AD 8700+2
Mar AD 1500 – Feb AD 1600−1Mar AD 5100 – Feb AD 52000Mar AD 8700 – Feb AD 8800+1
Mar AD 1600 – Feb AD 28000Mar AD 5200 – Feb AD 6400+1Mar AD 8800 – Feb AD 10000+2
Mar AD 2800 – Feb AD 2900+1Mar AD 6400 – Feb AD 6500+2Mar AD 10000 – Feb AD 10100+3
Mar AD 2900 – Feb AD 32000Mar AD 6500 – Feb AD 6800+1Mar AD 10100 – Feb AD 10400+2
Mar AD 3200 – Feb AD 3300+1Mar AD 6800 – Feb AD 6900+2Mar AD 10400 – Feb AD 10500+3
Mar AD 3300 – Feb AD 36000Mar AD 6900 – Feb AD 7200+1Mar AD 10500 – Feb AD 10800+2
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In 900 Julian years there are = 225 leap days. The Revised Julian leap rule omits seven of nine century leap years, leaving leap days per 900-year cycle. Thus the calendar mean year is 365 + days, but this is actually a double-cycle that reduces to 365 + = 365.24 days, or exactly 365 days 5 hours 48 minutes 48 seconds, which is exactly 24 seconds shorter than the Gregorian mean year of 365.2425 days, so in the long term on average the Revised Julian calendar pulls ahead of the Gregorian calendar by one day in 3600 years.
The number of days per Revised Julian cycle = 900 × 365 + 218 = 328,718 days. Taking mod 7 leaves a remainder of 5, so like the Julian calendar, but unlike the Gregorian calendar, the Revised Julian calendar cycle does not contain a whole number of weeks. Therefore, a full repetition of the Revised Julian leap cycle with respect to the seven-day weekly cycle is seven times the cycle length = 7 × 900 = 6300 years.