The Mysterious Calendar of the Dwarves

Browse through Appendix D of The Lord of the Rings, and you'll discover in great detail how the calendars of Hobbits, Men and Elves worked. Strangely, though, Tolkien has nothing to say there about Dwarves: the only clues we have to their calendar are from Thorin's words quoted in The Hobbit.

As so often with Tolkien, though, we can deduce an awful lot from one sentence. It's clear that the Dwarves had a lunar calendar. Our modern calendar, and all those described in Appendix D, are solar calendars: they're based on the Sun's annual motion through the sky. There is an alternative, though: it's possible to design a calendar based on the phases of the moon, and the Dwarves must have used a calendar of this kind.

A lunar calendar works by breaking down time into periods of roughly four weeks, during which the moon changes from new to full to new again. This approach has one big advantage that solar calendars lack - the face of the moon acts like a gigantic 'sundial' marking out the passage of each 'lunar month'. You can see this in action in Sam's reaction after the Fellowship leave Lórien, and the Moon has an unexpected phase: 'either it's out of its running, or I'm all wrong in my reckoning' (The Fellowship of the Ring II 9 The Great River). Sam thinks of the moon in much the same way as a watch or clock, as have many peoples throughout history.

Regulating a calendar by the moon instead of the sun might be useful from one perspective, but it also has a big disadvantage. A lunar year (twelve lunar months) is only 354 days long: eleven days short of a solar year. For every solar year that passes, the calendar will 'slip' back by more than a week. This is much more than a technical inconvenience, because the passage of seasons follows the solar year, not the lunar. Any given date will 'shift' by six months every seventeen years or so - midsummer becomes midwinter in less than a generation.

The Dwarves seem to have taken a direct approach to this problem - they reset their calendar every single year. When Thorin says that their year starts on 'the first day of the last moon of Autumn', what he means is that the Dwarves find a point where the lunar and solar (seasonal) calendars coincide, and restart their calendar from that point.

Perhaps the most curious outcome of this is that Dwarvish years have a variable number of months, sometimes twelve, and sometimes thirteen. Tolkien doesn't mention this 'leap month' (which would occur quite often) directly, but it must have occurred².

Another peculiarity of the Dwarves' calendar relates to Durin's Day itself. In most cases, only Dwarves at the right longitude will experience Durin's Day. A perfect example is the Durin's Day we know occurred in 2941 of the Third Age (the one described in The Hobbit). As with most Durin's Days (eclipses are an exception), the moon and sun can only be seen together in the early morning or late evening. Bilbo saw the crescent moon as the sun was setting over Erebor.

Erebor, though, is in the distant east of Middle-earth. At the time Bilbo was seeing 'a thin new moon above the rim of the Earth.' (The Hobbit 11, On the Doorstep), the Sun was still fairly high in the sky over the Blue Mountains, a thousand miles or more to the west. By the time the sun was low enough for the Dwarves in the Blue Mountains to see the moon, it would already have set! It was Durin's Day for the Dwarves at Erebor, then, but not for their cousins in the west.

We can hardly blame Thorin for saying 'it passes our skill in these days to guess when such a time will come again'! (The Hobbit 3, A Short Rest)

Everything we've said here follows unavoidably from Thorin's few comments in The Hobbit. What we can't say, of course, is whether Tolkien realized these astronomical consequences. He obviously had a very good understanding of how calendars work: the fictional calendars in Appendix D are beautifully constructed, and in some ways an improvement on our own. The ancient idea of exactly aligning a calendar with the solstices and equinoxes, for example, is the basis for many of Tolkien's calendars - the modern Gregorian system is 'out' by ten days or so.

It seems hard to believe that Tolkien would expend such effort on the development of calendars for Hobbits, Men and Elves, and yet forget the Dwarves completely. Perhaps he took a look at their calendar and decided it was too awkward to describe in detail, but if he did, he has left us no evidence.