Here is a reprint of a piece I have shown several times.
ABSTINENCE IN THE EASTER OCTAVE
It was Pius XII who levelled out the Octaves by making all the days Doubles of the First Class, or, as some of you might nowadays say, Solemnities. Such days, canonically, do not admit Abstinence. So one is not bound to Abstinence on the Friday after Easter.
ABSTINENCE IN THE PENTECOST OCTAVE
What about Abstinence on Pentecost Friday? I repeat below a ruling by the CBCEW to the effect that Abstinence is "contrary to the mentality of an octave". But the Friday in the Pentecost Octave survives in the EF but not in the OF! Here, surely, we have a juridical gap.
My view is that, in communities or families in which the dominant "Form" is the EF, the Friday is, according to the legislation in the 1962 books, and the statement of the English and Welsh bishops, a day which excludes Abstinence. (There is, of course, a bit of an oddity in this, in as far as this Friday is an Ember Day on which historically Catholics fasted. But that was a long time ago.)
ABSTINENCE IN THE CHRISTMAS OCTAVE
On 16 October 2014, the Catholic Herald announced that a spokesperson of the CBCEW had stated that Boxing Day, which in 2014 was a Friday, is not a day of Abstinence. "To consider St Stephen's Day or Boxing Day as a day of abstinence would not be compatible with the festive and celebratory nature of the Christmas Octave ... An octave is an ongoing celebration of the two highest ranking solemnities of the Liturgical Year ... it is contrary to the mentality of what an octave is to consider one of its days as penitential ... Octaves are weeks of joy, not abstinence, even though the Easter Octave ranks unambiguously higher than that of Christmas."
There is no doubt that local hierarchies do have the canonical right to make rules about Abstinence (Canon 1253 Episcoporum conferentia potest pressius determinare observantiam ... ieiunii et abstinentiae ...).
Interestingly, the statement makes clear that the ruling applies not just to a Boxing Day which falls on a Friday, but, every year, to whichever day in the Octave of Christmas is a Friday*.
When I first published a version of this, some people got worried about whether the CBCEW spokesman was misleading them. Two basic rules of Traditional Catholic Moral Theology: (1) Doubtful laws do not bind. In other words, if there is some doubt whether a law applies to me ... it doesn't. If the Bishops say it doesn't apply to me, then their statement creates at least an objective doubt as to whether it applies to me
(2) We are NOT obliged to be Rigorists, Tutiorists, or Probabiliorists. The Church condemned the Jansenists. If there is a genuine doubt between two possibilities, one is entitled to exercise one's free choice.
That is what the pre-Conciliar books on Moral Theology say.
Not that there is any doubt in this matter. YOU NEED NOT ABSTAIN FROM MEAT ON THE FRIDAY AFTER CHRISTMAS, IF YOU LIVE IN ENGLAND OR WALES.
* Where a National or Diocesan or Ordinariate or Parochial Patron is observed as a Solemnity and falls on a Friday, that Friday is not a day of Abstinence.