15th November (geez calander), marks the first day of the Advent Fast, a period of abstinence and penance practiced by the Church from ancient times, in preparation for the Nativity of Christ. This fast, is observed beginning on November 15th and ending on Christmas Eve, with the Feast of the Birth of Christ (Christmas). It is a time for devout and penitential preparation of the soul for the proper and worthy celebration of the great feast of Christmas.

Fasting is abstinence from all things that a body needs, and one has to fast from animal products and from any kind of food for a limited time until the period of fasting is over. (Mt. 6:16, Fetha Negest 15). In general, one has to abstain from anything which the body desires.
The aim of fasting is to make the desire of the body to obey the will of the soul, to seek forgiveness of guilt and to increase the reward of the Soul.