In my casual reading of several oriental calendars I noticed the terms "Holy Day of Obligation" was use to denote high and great feasts of the church and the inclusion of the Feast of the Immaculate Conception in the liturgical calendar.
Which Oriental Churches celebrate the Immaculate conception feast, how is it understood by them, and what were the factors in choosing to elevate and celebrate it liturgically?
Also, how prevalent is the term "Holy Day of Obligation" in the East? I know some byzantine jurisdictions don't use it or prefer not to, and others do. Do all or most of the oriental catholics use this term?
Thanks!