Personal warning - this Tab S is my first Android device so I'm new and still somewhat lost. When I saw this thread/question the other day I wanted a Calendar widget.
I did not see any Calendar Widget in the native choices. I downloaded one.
I have to admit, I'm still not sure how to use those "PAGES" where widgets are located. I guess you can create Favorites and those various pages can have widgets???? I still tend to generally use the pages that have ALL my icons (opened by using the checker-grid in the lower right corner).