The fasting rules, found for the most part in the Typikon (mainly Chapters 32 and 33), and repeated in appropriate places of the Menaion and Triodion, are dependent on the Church's cycle of feasts and fasts. In general, with a few exceptions, all Wednesdays and Fridays (Mondays also, in some monasteries) are kept as days of fasting, with no meat, eggs, dairy products, fish, wine or oil to be eaten. This includes, as well, the four canonical fasting periods (Great Lent, the Apostles' Fast, the Nativity Fast and the Dormition Fast), and certain other days, including the Eve of Theophany, the Beheading of St. John the Baptist, and the elevation of the Cross. It must be noted, however, that there are many local variations in the allowances of wine and oil (and sometimes fish), such as on patronal feast days of a parish or monastery, or when the feast of a great Saint (or Saints) is celebrated which has particular local or national significance.
While most Orthodox Christians are perhaps aware of the rules of fasting for Great Lent, Wednesdays and Fridays, the rules for the other fasting periods are less known. During the Dormition Fast, wine and oil are allowed only on Saturdays and Sundays (and sometimes on a few feast days and vigils). During the Apostles' Fast and the Nativity Fast, the general rules are as follows (from Chapter 33 of the Typikon):
It should be noted that in the Fast of the Holy Apostles and of the Nativity of Christ, on Tuesday and Thursday we do not eat fish, but only oil and wine. On Monday, Wednesday and Friday we eat neither oil nor wine…. On Saturday and Sunday we eat fish. If there occur on Tuesday or Thursday a Saint who has a Doxology, we eat fish; if on Monday, the same; but if on Wednesday or Friday, we allow only oil and wine…. If it be a Saint who has a Vigil on Wednesday or Friday, or the Saint whose temple it is, we allow oil and wine and fish…. But from the 20th of December until the 25th, even if it be Saturday or Sunday, we do not allow fish.
In another place the Typikon prescribes that if the Eve of Theophany or the Eve of the Nativity fall on Saturday or Sunday, wine and oil are permitted.
The rule of xerophagy is relaxed on the following days:
1. On Saturdays and Sundays in Great Lent, with the exception of Holy Saturday, two main meals may be taken in the usual way, around mid-day and in the evening, with wine and olive oil. Meat, animal products and fish are not allowed.
2. On the Feast of the Annunciation (March 25) and Palm Sunday fish is permitted as well as wine and oil, but meat and animal products are not allowed.
3. Wine and oil are permitted on the following days, if they fall on a weekday in the Second, Third, Fourth, Fifth or Sixth Weeks: First and Second Finding of the Head of St. John the Baptist (Feb. 24), Holy Forty Martyrs of Sebaste (Mar. 9), Forefeast of the Annunciation (Mar. 24), Synaxis of the Archangel Gabriel (Mar. 26), Holy Greatmartyr George (April 23), Holy Apostle and Evangelist Mark (April 25), as well as the Patronal Feast of a Church or Monastery.
4. Wine and oil are also allowed on Wednesday and Thursday of the Fifth Week, because of the Vigil for the Great Canon. Wine is allowed and, according to some authorities, oil as well on Friday in the same week, because of the Vigil for the Akathist Hymn.
It has always been held that these rules of fasting should be relaxed in the case of anyone elderly or in poor health. Personal facts also need to be taken into account, as, for example, the situation of an isolated Orthodox living in the same household as non-Orthodox, or one obliged to take meals in a factory or school lunchroom. In cases of uncertainty, however, one should always seek the advice of his or her spiritual father.
At all times, however, it is essential to bear in mind that you are not under law but under grace (Rom. 6:14), and that the letter kills, but the Spirit gives life (2 Cor. 3:6). The fasting rules, while they do need to be taken seriously, are not to be interpreted with the strict legalism of the Pharisees of Holy Scripture, for the kingdom of God is not food and drink, but righteousness and peace and joy in the Holy Spirit (Rom. 14:17).