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The '''Revised Julian Calendar''' is a calendar that was considered for adoption by several Orthodox churches at a [[synod]] in Constantinople in May 1923. The synod synchronized the new calendar with the [[Gregorian Calendar]] by specifying that [[October 1]] , 1923 , in the [[Julian Calendar]] will be [[October 14]] in the Revised Julian Calendar, thus dropping thirteen days. It then adopted a leap year rule that differs from that of the Gregorian calendar: Years evenly divisible by four are leap years, except that years evenly divisible by 100 are not leap years, unless they leave a remainder of 200 or 600 when divided by 900, in which case they are leap years. This means that the two calendars will first differ in 2800, which will be a leap year in the Gregorian Calendar, but a common year in the Revised Julian Calendar. T his This leap year rule was proposed by Milutin Milankovic, an astronomical delegate to the synod representing the governments of the Serbs, Croatians, and Slovenes.
Milankovic selected this rule, which produces an average year length of 365.242222… days, because it was within two seconds of the then current length of the ''mean'' tropical year. However, the ''vernal equinox'' year is slightly longer, so for a few thousand years the Revised Julian Calendar doesn't do as good a job as the Gregorian Calendar at keeping the vernal equinox on or close to [[March 21]]. But the length of a day is increasing by about 1.7 milliseconds per century (due to tidal acceleration), so the number of days per year decreases by about 0.0001 each millennium. This means that in the long run, the Revised Julian Calendar will also be inaccurate even if the mean tropical year is the basis.
==Reference==
*Miriam Nancy Shields, "The new calendar of the Eastern churches", ''Popular Astronomy'' 32 (1924) 407-411. This is a translation of M. Milankovitch, "The end of the Julian calendar and the new calendar of the Eastern churches", ''Astronomische Nachrichten'' No. 5279 (1924).
==See also==
*[[Paschalion]]
[[Category:Church History]]
[[Category:Liturgics]]
