*The '''[[Gregorian Calendar]]''', a calendar introduced in 1582 by Pope Gregory XIII of the [[Roman Catholic Church]] and used in the Churches of [[Church of Finland|Finland]] and [[Church of Estonia (Ecumenical Patriarchate)|Estonia]].*The '''[[Revised Julian Calendar]]''', the calendar considered by a [[synod]] of Orthodox churches in 1923 in Constantinople. This is functionally identical to the Gregorian Calendar except for the [[Pascha]]l cycle (which is still [[Paschalion|reckoned]] according to the [[Julian Calendar|Julian]] timetables) and leap year calculation.