The church calendar according to which Orthodox Christians celebrate religious feasts is based on the Julian solar calendar consisting of two main parts – “immovable” and “movable”. The immovable part, Menologion, contains dates of immovable Orthodox feasts which fall on the same day every year. The movable part, Paschal tables, contains the circle of movable Orthodox feasts, the calculation point is the main holiday – Easter or the Resurrection of Christ. Paschal tables were adopted by the First Ecumenical Council which was held in 325 in Nicaea, a town in Bithynia, Asia Minor. The Council of Nicaea established the basic rules for annual calculation of the movable Orthodox Easter date. It is not easy to do the right calculation. One should use a number of tables with different interrelated calendar values. “Indiction”, “Solar cycle”, “Metonic cycle”, “Easter limits” – these are the names of some of the tables. Their annually changing values are essential to calculate the exact Easter date. To realize these calculations in mechanics is a challenging task. Timepieces by Konstantin Chaykin from the collection “Orthodox Timepieces” can calculate and indicate the date of Orthodox Easter due to the integrated unique invention of the craftsman.
Astronomical clock “Resurrection” with Easter calendar