Every day of the octave of Easter is a first class feast. It is a continuation of the Easter festivity. You don't fast and abstain on those. (at least they don't at the seminary). Likewise, for example, if Christmas fell on a Friday. In Gueranger's Liturgical Year, he said that in former times, the whole week was a feast where Christians rested from servile labor. Legal proceedings and military campaigns were put on hold.