As a traditional Lutheran you might appreciate the plight of traditional Catholics these days. Traditionally, Ascension Thursday (sometimes called "Ascension Day") is always on the Thursday following the 5th Sunday after Easter (or "Resurrection Sunday"). In the count, the first Sunday in included because Jesus rose in the early morning. 5x7+1=36, the number of days at the 5th Sunday. Plus four more takes you to Thursday at 40 days after Easter.
Traditionally, Jesus ascended into heaven on a Thursday, just as He rose from the dead on a Sunday.
But this is talking about Ascension Thursday, while this thread is talking about the Assumption of the Blessed Virgin Mary, traditionally commemorated on August 15th, whichever day in the week that falls on, even Sunday. This year it falls on Monday, but a few years ago the American bishops decided to make Monday and Saturday observance optional in some such cases. Traditional Catholics don't look for ways of escaping the traditional norms, so we show up for Mass on Monday like Catholics would have done before the recent convenience-related revisions.
If Monday and Saturday are too inconvenient, why stop there? Tuesday and Friday might be too inconvenient next year, and after that, Wednesday and Thursday might suddenly rise to the modern norm of inconvenience. After that, well, what's so special about Sunday? The logical end excludes all seven days of the week as too inconvenient for attendance at Mass.
The 24/7 retail world has gutted any real observance of the 3rd Commandment (Luther's numbering, 4th for everyone else) so it is no surprise that trying to maintain any other days as holy is a real upstream swim. The sad truth is that many children are growing up believing that Church "happens" only on Sundays, except perhaps for Christmas Eve.