I intend to incorporate your code into an app I am creating for a friend who wants to be an author.  As your seed program shows, it can be easy to overload the viewer.  To simplify, I plan to add to the event record a couple of additional fields, and provide a mechanism preferably on the calendar itself where the additional fields would have collection_select menus for the new event record entries (multiple selections allowed).  He could then have calendar views for specific objects (characters, story plot, etc.).  In addition, one of the fields would hold an 'offset' value which would override the Date.today and move it forward/backward in time.   Thus if he were writing a period piece about the 15th century, I would expect the calendar for that selected calendar year would show up in the calendar view; i.e., "Feb 2017" would become "Feb 1517" if the offset were -500 years.

Doing a code search for date variations does not show me where that banner date value is being generated.  

Any hints or comments that you or your viewers might be willing to share?

Thanks