I just have an update on this. I did the time cheat to make time go by fast, and regardless of the number of the days on the calendar, the first 4 weeks will always show the school, prom, etc icons. So, all though they don't show past that on a calendar setting of 14 or 28, they will still remain on the calendar as the first 4 weeks once your date reaches that. I haven't tested the going to school part or the school events, but at least the icons letting you know that the HSY events are still always going to be there on the calendar.
@SilentKitty I am only using a CC mods with a few basic other mods, but nothing that manipulates the game drastically like MCCC. I took that out.
@RavenSpit I did notice that the school days where scheduled beyond the 4 weeks and showed on the calendar as well, but it was the school icons like football, cheerleading, prom, etc that weren't showing beyond the first 4 weeks. However, as mentioned above, although they don't show on the calendar beyond the first 4 weeks, they will still always remain on the calendar as the first 4 weeks when that time comes beyond the first 4 weeks. So, I guess that's a good thing. I just need to actually test if they still work on the long life span and ageing off options.