This is a problem for me too, but in only my main save file that I have been playing for over 2 years. I thought it might be a mod issue so I tested it mod free in a new save, the events were on the calendar so I started to 50/50 my mods to find the culprit and couldn't find it. I started another new save with all my mods, and the events were on the calendar just fine with all my mods.
I removed mods from my main save and opened it, played for a bit and there was still no GF events on the calendar. this issue only shows up in my 2+ year old save file.
If you saved in that state the change is now permanent in that save.
