If I go to the main website and open the email with the invite I get a preview of the invite and I can click to add it to my calendar. On the phone I see the attachment of the .ics file and when I click it I get asked what I want to open it with.

I guess I don't really know if I am using the Google calendar mine is just called calendar too.

It would be nice if I could tell where theses programs are from.