Hi!
In my use-case, when the national grid tells us (API sensor) that there is a forthcoming power saving event, I’d like Home Assistant to create a local calendar entry for it. When said event comes up, it would trigger an actionable notification on my phone which I could press to initiate my power saving automation.
The key thing here is that I need to be able to programatically create Calendar Events, preferably using a service call.
Yeah I’d like to add this using a similar service as provided by Google calendar today, but that works for any calendar that supports creating event.
Agreed. This would be great 
Would LOVE this feature too. My use case is scanning NFC Tags on things that need regular maintenance. Think replacing the HVAC air filter or cleaning out the washing machine.
Do the chore, scan the tag, and a new calendar event is created X days in the future to remind you again.
I have the same use case with using a calendar for regular maintenance combined with NFC tags. Would be very good if we could add, edit and delete events in an automation.
I hope that we get a “delete” option soon.