What's with the Calendar App?

[AC Question]

What’s the deal with the Samsung calendar app? Mine has taken over, so I apparently cannot install and use the Google calendar I’m used to. Then it sends out notifications on everything, using up my battery. When I go into App Manager to fix that (or delete it), the program is not even listed! It’s some kind of phantom I can’t track down to fix or elimiate! Any ideas? (At least I guess it’s a Samsung app—Just an app named “Calendar”, and and icon showing a “31” in a square with a green bar across the top)
THANKS