non-leap) and then add back in the number of prior century leap years: PriorCenturies = floor(PriorYear / 100) FixedDays = FixedDays − PriorCenturies + floor((2 × PriorCenturies + 6) / 9) Fixed days to Revised Julian Convert an ordinal day number to the corresponding Revised Julian year, month, and day, starting by removing any fractional time-of-day portion: Days = floor(FixedDays) − RJepoch + 1 PriorCenturies = floor(Days / 36524) RemainingDays = Days − 36524 × PriorCenturies - floor((2 × PriorCenturies + 6) / 9) PriorSubcycles = floor(RemainingDays / 1461) RemainingDays = RemainingDays MOD 1461 PriorSubcycleYears = floor(RemainingDays / 365) year = 100 × PriorCenturies + 4 × PriorSubcycles + PriorSubcycleYears RemainingDays = RemainingDays MOD 365 IF RemainingDays = 0 THEN This is either the 365th day of a common year, or the 365th or 366th day of a leap year. Either way, we have to decrement the year because we went one year too far: year = year − 1 IF isLeapYear(year) AND PriorSubcycles=0 THEN RemainingDays=366 ELSE RemainingDays=365 END IF PriorDays = RemainingDays − 1 IF isLeapYear(year) THEN correction = 1 ELSE correction = 0 IF PriorDays < (31+28+correction) THEN correction = 0 ELSE correction = 2 − correction Month = floor((12 × (PriorDays + correction) + 373) / 367) Finally, calculate the day number within the month by subtracting the Fixed days count for the start of the month from the originally given Fixed days count, and then add one day: Day = FixedDays - RevisedJulianToFixed(year, month, 1) + 1 Fixed days to weekday number Convert the ordinal number of days since the Revised Julian epoch to a weekday number (Sunday=1 through Saturday = 7): WeekdayNumber = (floor(FixedDays) − RJepoch + 1) MOD 7 + 1 Don't be tempted to omit subtracting the RJepoch just because it is offset by adding +1. As written, this expression is robust even if you assign a value other than one to the epoch. References Notes Citations Sources This is a translation of the paper in Astronomische Nachrichten. External links The Calendar of the Orthodox Church by Lewis J. Patsavos The "Revised" Julian Calendar: Memorandum of Explanation by the Holy Synod (Orthodox Church in America) Liturgical Havoc Wreaked by the "New Julian" Calendar by Hieromonk Cassian The Essence of the Church Calendar On the Question of the "Revised Julian Calendar" by George Lardas The 70th Anniversary of the Pan-Orthodox Congress, Part I of