OK, thanks.
Summary:
-You have two iPads, one is an iPad Air
-Both running iOS 10.2
-iPad Air has Hotmail account setup, the other has no accounts setup
Questions:
-Are you using iCloud on both iPads?
-Are there a lot of calendar events?
-If using iCloud, do you have a Mac that is also signed in with the same Apple ID? If so, does the calendar app work properly on it?
We'll try and narrow this down.
C