Middle-earth Calendar - Durin's Day

Durin's Day

Durin's Day is a rare event noted by Dwarves. The first day of the Dwarves' year is the day that begins the last cycle of the Moon, starting with a New Moon, to begin in Autumn. When on this day both the Sun and Moon may be seen in the sky together, it is called Durin's Day. Each lunar cycle takes about 29.5 days. When Autumn in the northern hemisphere is assumed to start on the autumnal equinox, generally on September 22, the season runs until about December 21. The first day of the last new moon of Autumn could thus take place any time between about November 22 and December 21.

However, the seasons in Tolkien's work have the four solar markers at the centre of the seasons, not the beginning. For example, Midsummer occurs on the summer solstice, Midwinter on the winter solstice, etc. Autumn would therefore begin midway between the summer solstice and the autumnal equinox, around August 6, and end midway between the autumnal equinox and the winter solstice, around November 6. That places the Dwarves' New Year, anytime between about Oct. 7 and Nov. 6, on the last day before the astronomical new moon as the moon sets just before the sun.

In The Hobbit, the writing on the map that Gandalf had received from Thráin II mentioned Durin's Day. It predicted that on Durin's Day the last light of the Sun as night fell would reveal the secret door into the Lonely Mountain.