Changes

The '''Revised Julian calendarCalendar''' is a [[calendar]] that was considered for adoption by the [[Eastern Orthodoxy|Eastern several Orthodox]] churches at a synod in [[Istanbulsynod]] in Constantinople in May [[1923]]. The synod synchronized the new calendar with the [[Gregorian calendarCalendar]] by specifying that [[October 1 October]] [[1923]] in the [[Julian calendarCalendar]] will be [[October 14 October]] in the Revised Julian calendarCalendar, 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, then 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 calendarCalendar, but a [[common year]] in the Revised Julian calendarCalendar. This T his 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 Calendar doesn't do as good a job as the Gregorian calendar Calendar at keeping the vernal equinox on or close to [[March 21]]. But the length of a [[day]] is increasing by about 1.7 [[millisecond]]s milliseconds per century (see [[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 Calendar will also be inaccurate even if the mean tropical year is the basis.

The Revised Julian calendar was adopted by the Orthodox Churches of [[Orthodox Church of Constantinople|Constantinople]], [[Orthodox Church of Alexandria|Alexandria]], [[Orthodox Church of Antioch|Antioch]], [[Church of Greece|Greece]], [[Orthodox Church of Cyprus|Cyprus]], [[Romanian Orthodox Churchof Romania|Romania]], [[Polish Orthodox Churchof Poland|Poland]], and [[Bulgarian Orthodox Churchof Bulgaria|Bulgaria]] (the last in [[1963]]), called the [[''''New calendarists]]Calendarists''''. It was rejected by the Orthodox Churches of [[Orthodox Church of Jerusalem|Jerusalem]], [[Russian Orthodox Churchof Russia|Russia]], [[Serbian Orthodox Churchof Serbia|Serbia]], and the [[Greek Old Calendarists]]. Despite the fact that the Russian Orthodox Church continues to use the Julian calendar Calendar for both its fixed festivals and for Easter, Milankovic stated that it had already adopted the new calendar by October 1923! (It must have repudiated its decision shortly thereafter.)

The synod also adopted an astronomical rule for [[EasterPascha]]: Easter Pascha is the Sunday after the midnight-to-midnight day at the meridian of the [[Church of the Holy Sepulcher in [[Sepulchre (Jerusalem)|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. However, all Eastern Orthodox churches rejected this rule and continue to use the Julian calendar Calendar to determine the date of Easter Pascha (except for the [[Finnish Orthodox Churchof Finland]], which now uses the Gregorian EasterPascha).