from Wikipedia article on Lent:
en.wikipedia.org/wiki/Lent


Fasting and abstinence

Fasting during Lent was more severe in ancient times than today. Socrates Scholasticus reports that in some places, all animal products were strictly forbidden, while others will permit fish, others permit fish and fowl, others prohibit fruit and eggs, and still others eat only bread. In some places, believers abstained from food for an entire day; others took only one meal each day, while others abstained from all food until 3 o'clock. In most places, however, the practice was to abstain from eating until the evening, when a small meal without meat or alcohol was eaten.

During the early Middle Ages, meat, eggs and dairy products were generally proscribed. Thomas Aquinas argued that "they afford greater pleasure as food [than fish], and greater nourishment to the human body, so that from their consumption there results a greater surplus available for seminal matter, which when abundant becomes a great incentive to lust."[8]

However, dispensations for dairy products were given, frequently for a donation, from which several churches are popularly believed to have been built, including the "Butter Tower" of the Rouen Cathedral. In Spain, the bull of the Holy Crusade (renewed periodically after 1492) allowed the consumption of dairy products[9] and eggs during Lent in exchange for a contribution to the conflict.

Giraldus Cambrensis in his Itinerary of Archbishop Baldwin through Wales reports that "in Germany and the arctic regions," "great and religious persons," classified the tail of beavers as "fish" because of its superficial resemblance to a fish and their relative abundance.

In current Western societies the practice is considerably relaxed, though in the Eastern Orthodox, Oriental Orthodox and Eastern Catholic Churches abstinence from the above-mentioned food products is still commonly practiced, meaning only vegetarian meals are consumed during this time in many Eastern countries. Lenten practices (as well as various other liturgical practices) are more common in Protestant circles than they once were. In the Roman Catholic Church it is tradition to abstain from meat from Ungulates (meaning roughly "being hooved" or "hooved animal") every Friday for the duration of Lent, although dairy products are still permitted. On Ash Wednesday it is customary to fast for the day, with no meat, eating only one full meal, and if necessary, two small meals also.[10]

Contemporary legislation is rooted in the 1966 Apostolic Constitution of Pope Paul VI, Paenitemini. He recommended that fasting be appropriate to the local economic situation, and that all Catholics voluntarily fast and abstain. He also allowed that fasting and abstinence might be substituted with prayer and works of charity.

Pursuant to Canon 1253, days of fasting and abstinence are set by the national Episcopal conference. On days of fasting, one eats only one full meal, but may eat two smaller meals as necessary to keep up one's strength. The two small meals together must sum to less than the one full meal. Parallel to the fasting laws are the laws of abstinence. These bind those over the age of fourteen. On days of abstinence, the person must not eat meat or poultry. According to canon law, all Fridays of the year, Ash Wednesday and several other days are days of abstinence, though in most countries, the strict requirements of abstinence have been limited by the bishops (in accordance with Canon 1253) to the Fridays of Lent and Ash Wednesday. On other abstinence days, the faithful are invited to perform some other act of penance.

Many modern Protestants consider the observation of Lent to be a choice, rather than an obligation. They may decide to give up a favorite food or drink (e.g. chocolate, alcohol) or activity (e.g., going to the movies, playing video games, etc.) for Lent, or they may instead take on a Lenten discipline such as devotions, volunteering for charity work, and so on. Roman Catholics may also observe Lent in this way in addition to the dietary restrictions outlined above, though observation is no longer mandatory under the threat of mortal sin. Many Christians who choose not to follow the dietary restrictions cite 1 Timothy 4:1-5 which warns of doctrines that "forbid people to marry and order them to abstain from certain foods, which God created to be received with thanksgiving by those who believe and who know the truth."
Liturgical year
Western

* Advent
* Christmastide
* Epiphany
* Lent
* Easter Triduum
* Easter season
* Feast of the Ascension
* Pentecost
* Ordinary Time

Eastern

* Feast of Cross
* Nativity Fast
* Nativity
* Theophany
* Great Lent
* Pascha
* Pentecost
* Apostles' Fast
* Great Feasts
* Transfiguration
* Dormition
* Protection

When observing fasting or abstinence during Lent, regard must be paid to the fact that Sundays are Feast Days, so the fast or abstinence may be broken. If one counts the days from Ash Wednesday to the day before Easter Sunday, excluding the Sundays, one will see that there are forty of them, corresponding to the number of days Christ spent in the wilderness.