Unless I misunderstand, you seem to have asked the same question twice. The Calendar undergoes significant testing before it is released. Many at this Forum have been involved. You are welcome (and have been invited) to participate in that testing.
You are also welcome to identify and report specific bugs you find with enough detail that developers are able to duplicate them and prioritize them for resolution. In my experience, no matter how thoroughly code is tested before it is exposed to the user, the user will find something that has not been anticipated.
Even among those of us who use the Calendar in production, we continue to find scheduling scenarios that never were considered by any of us. Testing in Beta finds many of them. Swarm testing finds even more. And the user probably still has not found all of them.
But if the developers waited until all the problems were identified before release, we would not yet even have a calendar.