Durin's Day is a rare event noted by Dwarves.
The new year of their calendar was the last cycle of the Moon to begin in autumn, or in Thorin's words "the first day of the last moon of Autumn on the threshold of Winter". When on this day both the Sun and Moon may be seen in the sky together, it is called Durin's Day.
The Moon-letters written on Thrór's Map predicted that on Durin's Day the last light of the Sun as night fell would reveal the secret door into the Lonely Mountain.
Unlike The Lord of the Rings Tolkien left no precise timetable for the events of The Hobbit. However, in The History of The Hobbit, Tolkien set 19 October as the date of that year's Durin's Day.
Before the History some calculations were made. According to Andreas Möhn, the Durin's Day of T.A. 2941 occurred on 22 October of the Shire Calendar. This is based in the assumption that the orbital period of the moon, as described in The Lord of the Rings, was about 20 minutes shorter/faster than today.
Karen Wynn Fonstad made a rough estimation based purely on the traveling times and distances, without any astronomical calculations. She puts the Durin's Day on 30 October.
- ↑ J.R.R. Tolkien, The Hobbit, "A Short Rest"
- ↑ J.R.R. Tolkien, John D. Rateliff (ed.), The History of The Hobbit, Return to Bag-End, "The Fifth Phase", "Timelines and Itinerary", "iii. The Timeline Revisited", pp. 826,828
- ↑ Andreas Möhn, "The Moon and Durin's Day", lalaithmesp.blogspot.com (accessed 15 February 2018)
- ↑ Karen Wynn Fonstad (1991), The Atlas of Middle-earth, "The Hobbit", p. 100