Its not a "premium feature" if it is something the app used to already do and literally every other calendar app out there does. For example, you can no longer schedule a recurring event and are now being asked to pay extra to do that now. Thats a pretty basic calendar function, not some amazing new design idea this app is implementing that would be worth paying more for. There are a lot of calendar apps out there. This used to be my go to one but no more if they are going to now charge for basic calendar features.
Jstharris about Calendars: Planner & Organizer, v5.9.3