Why do events in secondary Google calendars appear in my primary calendar too?

Due to the original implementation of Google Calendars, and to provide consistency with Microsoft calendar behaviour, Cronofy adds the primary calendar as the event Organizer.

Unfortunately, this is a constraint that we can’t change.

Calendar services communicate via iCalendar messages, which are usually transported via email, and originally, Google was not providing routable emails for secondary calendars. To make accept/reject messages work, Google would add the primary calendar as the owner of events with attendees. As the primary calendar uses the account email address, iCalendar messages could be routed to it.

This matches similar behaviour in the Microsoft ecosystem, where the account creating an event must be the organizer in the attendees list too.

As of 2023, Google added extra routing and UI features to make the use of secondary calendars better for users by providing them with a routable email address. This allows events in secondary calendars to invite attendees without needing to add the account email address. While this is preferable as an end user, Cronofy adopting this would be a breaking change to our existing customers, who may rely on the behaviour between Google and Microsoft being the same and being consistent with Google’s original representation.