*(I.) CANONICAL ORDER
*1. The period of the Nativity Fast begins on November 15 (the day after the Feast of St. Philip, 14 November) and ends on 24 December.
*2. During this period, on Mondays, Wednesdays, and Fridays, we eat food without oil, but fish is permitted on the other days.
*3. By Tradition, the period during which we are permitted to eat fish begins on the Feast of the Entrance of the Theotokos (21 November) and ends on the Feast of St. Spyridon (12 December).
*4. On the Eve of the Nativity (24 December), we maintain a strict fast (xerophagy), unless the Eve falls on a Saturday or a Sunday, in which case we are allowed oil, wine, and shellfish, but not fish.
*5. On the Feast of the Nativity we are permitted to eat food of any kind, regardless of the day on which it falls.
*6. There is a parallel and well-attested tradition that the period during which fish is permitted extends as far as the commemoration of the Holy Prophet Daniel and the Three Youths (17 December), since, according to the ancient order, the Nativity Fast lasted for only seven days (18-24 December).
*7. There is yet another parallel tradition, also quite well attested, that fish is permitted only on Saturdays and Sundays. This was originally a stricter order enjoined by monastic Typika and was not applied universally.
*8. The aforementioned two parallel practices have always existed in the life of the Orthodox Church, but it has been left—“on the basis of unwritten Church Tradition”—to the charitable discretion and pastoral responsibility of spiritual Fathers to accommodate their pious spiritual children either to the stricter or to the more lenient regimen, depending on their spiritual and physical capacities.
*9. The possibility of such discretion is mentioned both by St. John of Damascus, who explicitly emphasizes that in questions of fasting, “we should obey…those who have been entrusted with leadership and with stewardship of the word,” and by the Permanent Synod convened under Patriarch Luke
Chrysoverges of Constantinople (twelfth century), which codified the Nativity Fast (and that of the Dormition of the Theotokos) and which furnished local Orthodox Bishops with very broad canonical authority in the application of ecclesiastical economy, whenever the need might arise: “If we are compelled to relax the fasts on account of bodily infirmity, the prescribed days of the fast may be shortened at the behest of the Bishop; for this, too, has been decreed on the basis of unwritten Church Tradition.”
*10. If a Hierarch has not publicly announced in advance, in the region of his jurisdiction or to the parishes Priests, the order of fasting to be observed during the forty-day period of the Nativity Fast, especially with regard to whether everyone is or is not permitted to eat fish on Tuesdays and Thursdays until December 17, the Faithful should consult their spiritual Fathers concerning this matter and should put their instructions into practice with confidence, as the Saints enjoin: “Do nothing without the Bishop.”  21 November 1997 (Old Style) Entrance of the Theotokos
*1. See (i) St. Anastasios of Antioch, Patrologia Græca, Vol. LXXXIX,
cols. 1389-1398/G. Rallis and M. Potlis (eds.), SÊntagma t«n Ye¤vn ka‹ ÑIer«n KanÒnvn [Compendium of the Divine and Sacred Canons] (Athens: G. Chartophylax, 1852-1859), Vol. IV, pp. 580-584;
*(ii) St. Theodore the Studite, Patrologia Græca, vol. XCIX, cols. 1693-1696;
*(iii) Nikon the Monk, Patrologia Græca, Vol. CXXVII, cols. 525D-528A/Rallis and Potlis, SÊntagma,
Vol. IV, p. 591;
*(iv) “TÒmow ÑEn≈sevw” [“Tome of Union”] (920), in Rallis and Potlis, SÊntagma, Vol. V, p. 8/Praktikå t«n ÑAg¤vn ka‹ Ofikoumenik«n SunÒdvn [Proceedings of the Holy Œcumenical Synods], ed. Spyridon Melias (Holy Mountain: Kalyve of the Venerable Forerunner Publications, 1981), Vol. II, p. 77a;
*(v) Theodore Balsamon, Patriarch of Antioch, Patrologia Græca, vol. CXXXVIII, cols. 941AD, 1001AC, 1335-1360/Rallis and Potlis, SÊntagma, Vol. IV, p. 419-421, 488, 565-579;
*(vi) St. Nicodemos the Hagiorite, ÑIerÚn Phdãlion [The Rudder], pp. 93-94 (note on the Sixty-ninth Apostolic Canon), pp. 387ff. (note on the Third Canon of the Council of Neocæsarea), and p. 728 (note on the Nineteenth Canon of St. Nicephoros the Confessor);
*(vii) Peter Moghila, Metropolitan of Kiev, Orthodox Confession, Part I: Question/Answer 88, in J. Karmiris (ed), Dogmatikå ka‹ Sumbolikå Mnhme›a t∞w ÉOryodÒjou Kayolik∞w ÉEkklhs¤aw [Dogmatic and Credal Statements of the Orthodox Catholic Church] (Graz, Austria: Akademische Druck u. Verlagsanstalt, 1968), Vol. II, p. 632.
*2. St. Theodore the Studite, Patrologia Græca, Vol. XCIX, col. 1696D.
*3. St. Theodore the Studite, Patrologia Græca, Vol. XCIX, col. 1696C, 1700C.
*4. St. Theodore the Studite, Patrologia Græca, Vol. XCIX, col. 1697A; St. Nicodemos the Hagiorite, Phdãlion, p. 92, n. 2.
*5. St. Theodore the Studite, Patrologia Græca, Vol. XCIX, col. 1697A.
*6. Theodore Balsamon, Patrologia Græca, Vol. CXXXVIII, cols. 941C, 1001B, 1357C/Rallis and Potlis,
SÊntagma, Vol. IV, pp. 420, 488, 579.
*7. Nicholas of Constantinople, Patrologia Græca, vol. CXI, col. 401B; St. Meletios the Confessor,
ÉAlfabhtalfãbhtow, Step 37, “Concerning Oneʼs Overall Diet” (ed. Monk Spyridon Lavriotes, p. 142); St. Nicodemos the Hagiorite, Phdãlion, p. 95, n.1, p. 728.
*8. St. John of Damascus, Patrologia Græca, vol. XCV, col. 68AB.
*9. Theodore Balsamon, Patrologia Græca, vol. CXXXVIII, cols. 941BC/ Rallis and Potlis, SÊntagma, ol. IV, p. 420.
*10. St. Ignatios the God-bearer, Patrologia Græca, Vol. V, col. 704A, col. 668B.
•The Nicholas of Constantinople cited in footnote 6 is Nicholas III Grammatikos (1084-1111); he is not to be confused with St. Nicholas I Mystikos (16 May) or Nicholas II Chrysoverges (16 December), also Patriarchs of Constantinople, both of whom flourished in the tenth century.
*II. GUIDELINES FOR THE NATIVITY FAST
*14 – St. Philip the Apostle: fish is permitted.
*15 – Beginning of the Fast: on Mondays, Wednesdays, and Fridays oil is not permitted.
* 15-20 – Fish is not permitted.
+21 – Entrance of the Theotokos: fish is permitted.
+ 22-12/12 Order 1:Fish is permitted only on Saturdays, and Sundays.
+ 22-12/17 Order 2: Fish is permitted on Tuesdays, Thursdays, Saturdays, and Sundays.
*25 – St. Catherine the Great Martyr: wine and oil are permitted.
*30 – St. Andrew the First-called Apostle: wine and oil are permitted.
*4 – St. Barbara and St. John of Damascus: wine and oil are permitted.
*5 – St. Sabbas the Sanctified: wine and oil are permitted.
*6 – St. Nicholas the Wonder-worker: wine and oil are permitted.
*9 – Conception of the Theotokos: wine and oil are permitted.
*12 – St. Spyridon of Trimythous: wine and oil are permitted.
+ 13-24 Order 1: fish is not permitted.
*15 – St. Eleftherios the Hieromartyr: wine and oil are permitted.
*17 – St. Daniel the Prophet and St. Dionysios of Zakynthos: wine and oil are permitted.
+ 18-24 Order 2: fish is not permitted.
*20 St. Ignatios the God-bearer: wine and oil are permitted.
*24 Eve of the Nativity: strict fast (xerophagy); but if it falls on a Saturday or a Sunday, wine and oil are permitted.
*25 +Nativity of our Savior: foods of any kind are permitted