J.R.R Tolkien’s fantasy world of Middle Earth is populated by many unusual races, for which the author created elaborate panoply of languages, poetry, cultures, and back-stories. Since Middle Earth is a medieval, pre-industrial society, Tolkien did not neglect to depict pre-industrial techniques for measuring the passage of time. In our modern society, we rely on artificial clocks and calendars to keep track of time for us, but our friends from Middle Earth had to rely on those natural timekeepers used throughout our own pre-industrial history . . . the Sun and Moon.

Most people in today’s modern world are not familiar with natural astronomical timekeeping, and the astronomy of The Hobbit usually goes unnoticed. The measuring of months is determined by seasonal variations of the Sun, and time of the month can be found by following the cycles of the Moon’s phases. If we know what to look for, we can find quite a number of references to astronomical timekeeping throughout The Hobbit and Tolkien’s other works.

We read that Bilbo and the dwarves began their adventure “one fine morning just before May.”1 The party tramped along uneventfully for a whole month, as Bilbo remarks on the next page that “it will soon be June.”2 Bilbo notes the time of the month by noticing that the darkness of night was falling and “a waning moon appeared above the hills between the flying rags.”2 The seasoned observer of the sky realizes that such a waning Moon can be seen rising shortly after sunset in the days immediately following the Full Moon, a bit more than two weeks through the lunar cycle of the month.

Later on, as the party approaches the house of Elrond in the Elvish town of Rivendell, we’re told that “the light became very dim, for the moon had not risen.”3 This helps us to see that perhaps only a week or two have elapsed, since the waning Moon rises later and later after sunset with each following night, and the Moon would not be visible at nightfall.

Bilbo arrived in Rivendell to the sound of Elvish singing “in June under the stars.”4 We’re not told exactly when in June, but we are told that the party “stayed long in that good house, fourteen days at least.”5 We are also told that “they were to go on again with the early sun on midsummer morning.”6 According to British custom, “midsummer” is a name for the summer solstice, which falls on June 21. We therefore conclude that the party arrived in Rivendell on June 7.

On midsummer’s eve, the night before Bilbo and the dwarves departed, we are informed that “the moon was shining in a broad silver crescent.”7 This tells us that the Moon has become a waxing crescent, maybe four or five days past the New Moon. This clue lets us know that Bilbo arrived in Rivendell under a waning gibbous Moon, which would have risen a little bit before midnight. Armed with all this information, we can conclude that Bilbo likely spotted that waning Moon on about May 30.

This manner of reckoning time by Moon phases may seem strange to a modern reader, but this is how days and weeks were actually tracked throughout all history, before the development of modern artificial methods of timekeeping. While such factoids might seem irrelevant today, they point out Tolkien’s attention to detail and his expertise of such matters as a Professor of Early Anglo-Saxon literature.

An interesting astronomical event occurs in Rivendell that has great importance for the entire adventure. On the night of their departure, the dwarves’ map was discovered to have “moon-letters”:

“What are moon-letters?” asked the hobbit, full of excitement.

“Moon-letters are rune-letters, but you cannot see them,” said Elrond, “not when you look straight at them. They can only be seen when the moon shines behind them, and what is more, with the more cunning sort it must be a moon of the same shape and season as the day when they were written. . . . These must have been written on a midsummer’s eve in a crescent moon, a long while ago.”8

The moon-letters included instructions for discovering the entrance to the dwarf city of Erebor, underneath the Lonely Mountain, which was in the possession of the evil dragon Smaug. These instructions taught that . . .

“The setting sun with the last light of Durin’s Day will shine upon the key-hole.”

“Then what is Durin’s Day?” asked Elrond.

“The first day of the dwarves’ New Year,” said Thorin, “is as all should know the first day of the last moon of Autumn on the threshold of Winter. We still call it Durin’s Day when the last moon of Autumn and the sun are in the sky together.”9

This is a clear reference to the time of the New Moon, which is traditionally reckoned to be the first appearance of the crescent Moon in the evening sky after being invisibly lost in the Sun’s glare at the end of the previous lunar month.

During the time of the New Moon, the Moon is very close to the Sun and rises around the same time as the Sun. Thus, the Moon crosses the sky with the Sun and is seen only in the evening after sunset, when the Moon itself is very near to setting.