You can create a regular calendar by adding the following to the OP of a topic: (with calendar enabled checked)
[calendar]
[/calendar]
And then all of the following posts with a description and date will get added to it. eg:
It's my birthday!
[date-range from=2022-12-20 to=2020-12-21 timezone="America/Boise"]
You can then grab a category id of where you want to display it more prominently from the end of the category URL, and the post id of the calendar topic (you can get this from the json) and add it to this setting:
The calendar item posts in these topics are the ones controlled by the delete expired event posts after setting. 
There’s more detailed info in the Discourse Calendar topic, though if you need extra help feel free to spin up a new #support topic too. 
Actually, this seems like a good juncture to slide this topic over to #support for its forever home now we know that the setting is working as expected. After I’ve updated the Calendar&Event literature it may be worthwhile creating new #ux or #feature topics to cover any missing ideas.