Calendar

Depicted is the calendar in the Du Bourg Book of Hours. Instead of listing the days of the months, the calendar lists the dates of the religious feasts of various saints. According to my research, this is yet another way to identify where a book of hours was created, as calendars would vary immensly. This is mostly due to the fact that each region would have its own local feasts for the saints that were patrons of that region. 

Indeed, the gallery Les Enluminures, from which Wheaton purchased the book used this to identify the location of where the book came from, in addition to looking at the Use in the Hours of the Virgin.

Text Sources:

Sandra Hindman, Book of Hours Catalogue, Ohio: Les Enluminures, 2000.

Russel Hale, "Inside a Book of Hours", Harry Ransom Center, The University of Texas at Austin. http://www.hrc.utexas.edu/enews/2010/june/booksofhours.html, accessed April 17, 2014. 

Image Source:

http://mdid.wheatoncollege.edu/result.aspx, accessed April 17, 2014