Is there a way to see a calendar in Photos?
It doesn't look like the calendar made it into Sierra.  However, there are other ways to search for photos using specific keywords.  From this Apple Support page, you can either use Siri or Search to find photos taken on a specific day, at a specific location, or with specific people:


  For information about how to search using keywords assigned to photos,
  see Find photos by
  keyword.
  
  Ask Siri. Say something like:
  
  
  “Show me photos of California”
  “Show me photos from April”
  “Show me beach photos”
  “Show me vacation photos”
  “Show me photos of Becky”
  
  
  Use the built-in Search Box in Photos:
  
  
  Click the search field in the toolbar.
  Type the search text in the search field.
  
  
  As you type, suggested searches appear below the search field. You can
  type multiple words separated by a space to search based on multiple
  criteria. For example, entering “California March” locates all photos
  in “California” taken in “March.
  
  
  
  Click an item in the suggested searches to see matching photos.