Is there a way to do this?
Can it be launched without user action?
Is it possible to launch my app from a calendar event?
You can create a URL and save it into a calendar event, and the user can tap it to go to your app, but there's no way of making the app open when a specific event time happens.
For privacy reasons, the user must invoke your app themselves.
Imagine the horrors if a nefarious app added multiple events to your calendar, and their app opened every few minutes.