Quite often if not in nearly every single case, an annual event that repeats on a specific month/day will appear on the wrong day, typically a day late. Case in point is 'Cinco de Mayo', which occurs on May 5 annually. This year and most prior years, it has appeared on the calendar on May 6. You can see this at this URL. This has actually been a problem for quite some time, predating Joomla 4. I've always just assumed it had something to do with time zones, but that would change its behavior based on the current time of day and it doesn't.