first of all: I love this software!
If I save an event with category e.g. birthday and if it's a reoccuring event, Rainlendar shows the number of years which have passed since the first year.
This is great, but would also be useful for other categories. E.g., I have an own category like "day of death" or even unnamed categories, where the number of passed years is of interest.
Maybe you can make "calculate number of passed events" as a per event option, which the user can choose if event is re-occuring.