Except in a sense it’s not quite universal when you have bishops in one country saying you must attend Mass on Nov 1 to be in obedience and avoid the mortal sin but in another country no, fine to not attend Mass on that day.
Hon, with respect, you are completely missing the whole point of what a holy day of obligation is, and what exactly the ‘mortal sin’ involved is.
Different countries, and indeed different bishops in a country, can ‘choose’ from the list of holy days that is held as the ‘norm’ by the church–just as, in the U.S., the bishops can give us an indult from the NORM of the Church–which is to abstain from meat on every Friday, in and out of Lent. An indult is a permission to make a specific ‘change’ for good reasons as PASTORALLY DETERMINED by the bishops.
So for example in my former diocese (Burlington VT) the holy day of obligation is Ascension THURSDAY. And in my current diocese (Richmond VA) the holy day has been transferred by the bishop to the following SUNDAY.
If I were in Vermont, I would have to go to Mass on Thursday of next week. Here–I do not. I may go on the Sunday and meet the "Thursday obligation’.
But the whole POINT of the holy day is not so much the day itself. Come on, we do not KNOW that Jesus was born on December 25 or that Mary was assumed on August 15. It is not the DAY which is important per se (the ‘exact’ day) but the Mass or the intention thereof, AND not every single country has the ‘intention’ for every single ‘normative’ holy day. The bishops have the POWER as PASTORS to choose what their ‘flock’ can and should focus on, and Rome gives them that power because Rome trusts the bishops to be, well, bishops. Leaders.
The point is, what your bishops decide you are ‘bound to’. It is the DISOBEDIENCE TO LAWFUL AUTHORITY which is the problem, not the LOCATION OF THE PERSON.
I simply don’t know how to make clearer what seems absolutely crystal to me-- that bishops have a lawful authority to make pastoral decisions for their flock, and that if you are a member of that flock, you are under the authority.
Now, you’ll say, But Tantum, what if you go visit your poor auld mither next week in Vermont? Won’t you have to go to Mass on Thursday up there even if you wouldn’t down in old Virginny? Well, yes, I would. Because as a GUEST in the diocese I am bound by that bishop’s rule. So again, it is not the place per se, it is the authority of the bishop where I happen to be at the time. It is not mortal sin because of PLACE but because of the AUTHORITY OF THE BISHOP which should not be defied.