Preceding every great Feast of the Church is a corresponding period of preparation. This preparation includes prayer and fasting. On Wednesday November 15/28 the Church begins the Nativity Fast which is broken on the Feast itself December 25/January 7. During this Fast we are permitted to have wine and oil every day save Wednesdays and Fridays. On Saturdays and Sundays from the Entry of the Theotokos, Nov. 21/Dec.4 until the Feast of St Spyridon, Dec. 12/25 we are also permitted to eat fish.
On the Feast of the Entry of the Theotokos we begin to chant in the Matins, the Katabasiai of the Nativity “Christ is born, glorify Him”. On the Feasts of St Andrew, Nov. 30/Dec. 13 and St. Nicholas, Dec. 6/19 we begin to chant various hymns for the Nativity. Two Sundays before the Nativity is dedicated to the Forefathers of Christ and on the Sunday before the Nativity we read the genealogies of Christ according to Luke during the Matins and according to Matthew during the Divine Liturgy.
From the Prefeast of the Nativity, Dec. 20/Jan. 2 until the Eve of the Nativity the Three-ode canons (Τριώδιοι κανόνες) modeled after the Three-ode canons chanted during Great Week are chanted during the Compline . On the Eve of the Nativity we chant the Royal Hour and celebrate the Vesperal Liturgy of St. Basil the Great. This year, since the Eve of the Nativity is on a Sunday, the Royal Hours are chanted on Friday and the Liturgy of St. Basil the Great is celebrated on the feast of the Nativity itself, instead of the eve.
Thus, through the various pre-festal hymns of the Church, scripture readings, and comparably eased fasting we should be sufficiently prepared to celebrate the Nativity according to the flesh of our Lord and Saviour Jesus Christ.