Lak,
As Vladyka Basil has noted, the 12 Great Feasts are those observed by Eastern Catholics (those of the Byzantine Rite Churches) and Eastern Orthodox. Pascha is not counted among the 12, as it is the Feast of Feasts. And, as he also remarked, the concept of “holydays of obligation” is historically unknown to us, although a few Churches have adopted the terminology (a leftover from the days of latinization).
The feasts differ in some regards when you speak of the Oriental Churches and the Maronites (some of whom do use the styling “holyday of obligation”). I have a full set of links for lists of the other Churches, but it’s on a hard-drive that is undergoing recovery at the moment. Here are those of the
Maronites, they will look familiar.
Many years,
Neil