What is a Calendar
In Airtable lingo, “Calendars” are just views and views are ways of looking at data. So you can have multiple views but there’s no need for them to communicate with each other since it’s the underlying data that changes what they display.
Linking Data Between Airtable Spreadsheets
Now if you end up having multiple spreadsheets of data within a base, and you need those sheets to communicate with each other, then that can be most easily accomplished through advanced linking.
Linking Data from Google to Airtable
Live linking data between an exterior service and Airtable likely requires integrations or the API.