Accessing calendar via Microsoft Graph API while the user is not signed in

Question

I need to be able to create and modify events in a user's outlook calendar from a background service on my server. The users should only need to define this calendar once in my web application (sign in to their Microsoft account). Afterwards my application needs to be able to modify it in the background without having the user to signed in.

Is there a way to grant those permissions to the server application with the Microsoft Graph API?

Answer 1

If you would like to update events without users, it is depending on the type of calendar that the event is in.

Application permissions are not supported for updating events in group calendar.

But Application permission(Calendars.ReadWrite) is supported for updating events in user calendar.