Hi Andrea

Take a look at:
https://developers.google.com/calendar/overview
Personally i prefer python or php.

You can use crontabs to trigger the 30min event.
https://docs.onion.io/omega2-docs/running-a-command-on-a-schedule.html

I don't really have any expirence with the calendar api, so I can't give you an example.
But I hope this may give u an idea on how to start.