The Nativity Fast or Philip's Fast during Advent (Pylypivka) traditionally begins November 15 and lasts through Christmas Eve. Some begin fasting after Vespers on November 14.
How to observe: Eat less than usual on all days and abstain from meat, eggs, and dairy products on all weekdays.
In addition to this, also abstain from fish, oil, and wine and alcohol (beer is allowed) on Monday, Wednesday, and Friday through December 8. Starting December 11, eat less and abstain from meat, eggs, dairy products, fish, oil, and wine and alcohol on all weekdays.
How should I observe? Pregnant and nursing mothers, young children, the sick, and the elderly are not obligated to fast and abstain. All others should fast and abstain as much as they can.
Pastoral Letter: You can read more about how to observe the fast in a pastoral letter from the Ukrainian Catholic bishops of the United States at the Ukrainian Catholic Eparchy of St. Josaphat website.