Deleted Pre-made Holiday simply reappear in next year

The ones you mentioned - lottery, rebate and new skill - aren't fixed events on the calendar though, those are the additional random ones that pop up to make the week more interesting. They don't show up on the calendar until a few days before they happen.

So they pop up on the calendar without notice by design, I'd say. So I wouldn't call this a bug. Maybe you should post this on the feedback section of the forums and suggest they add a toggle off option in the menu for dynamicly generated events?