If you change old calendar events (recurring ones, for example) and create new ones like this, then you can see alerts at farthest two days out:
Go to Calendar > + (or, find your old event) > Alert > Select Two Days Before (that's the farthest you can have an alert out. The span might change if you make all-day appointments.
Then, Notification Center will alert you two days before, or whatever the specified time.
