So, while on the subject of Casemate Books, I shd mention another of their recent releases that while not on Tolkien looks to be relevant re. one thorny recurring problem in Tolkien studies: Durin's Day.
The book in question is LIVING THE LUNAR CALENDAR, ed. Ben-Dov, Horowitz, & Steele
The description of the book itself sounds like it deals directly with the thorny issue that the Dwarves apparently shared with several real-world cultures: not knowing when their own New Year occurred:
Lunar calendars suffer from an inherent uncertainty in the length of each month and the number of months in the year. Variable atmospheric conditions, weather and the acuity of the eye of an observer mean that the first sighting of the new moon crescent can never be known in advance. Calendars which rely on such observations to define the beginning of a new month therefore suffer from this lack of certainty as to whether a month will begin on a given day or the next. The papers in this volume address the question of how ancient and medieval societies lived with the uncertainties of a lunar calendar. How did lack of foreknowledge of the beginning of the month impact upon administration, the planning of festivals, and historical record keeping?
So, it might be worthwhile for those interested in such topics (hi Gary!) to see if the pieces in this book shed any useful light on the topic. In any case, I'd be interested to hear their opinion thereon.