In the years leading up to the conclusion of Vatican II, the day before the Feast of the Immaculate Conception was commonly observed by Catholics in many countries as one of the few remaining days of both fasting and complete abstinence from meat. It was thus observed (as of 1962) in the United States, Canada, the United Kingdom, Ireland, the Philippines and some other countries.
Despite the reduction in the days of required fasting and abstinence with the promulgation of Paenitemini in 1966 followed by further reductions at the behest of national hierarchies, there exists no reason why Catholics -- especially those of a Traditionalist bent -- should not observe the older practices regarding fasting and abstinence. While some devout souls might want to go to greater lengths and keep all of Advent (except Sundays and some feast days) as a time of fasting and abstinence, others could start by keeping the fasts that existed in the years immediately before and during Vatican II. In December this would include not only December 7, but also the one-day fast just before Christmas Day (observed either on December 23 or 24 depending on the country).
There are also the Ember Days of Advent, which are of their very nature days of increased prayer and penance despite having been removed in many countries from the list of days for fasting and abstinence years before Vatican II, with the sole exception of Ember Friday as a day of complete abstinence (because it is a Friday).
There are also the Ember Days of Advent, which are of their very nature days of increased prayer and penance despite having been removed in many countries from the list of days for fasting and abstinence years before Vatican II, with the sole exception of Ember Friday as a day of complete abstinence (because it is a Friday).