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.
Read the Whole Article at http://liturgicalnotes.blogspot.com/