Update: Tolkien did use a 1940s calendar! Read more here.

An Introduction to Lunar Phases

As you perhaps noticed on the home page or in the archives, this site displays the phase of the moon for each day of the adventure in The Lord of the Rings. Since some readers will be curious how this site computes the phase of the moon, and others may even wish to do their own calculations, this page attempts to collect everything known about lunar phases in Tolkien's text.

The text of The Lord of the Rings usually offers only a partial description of the Moon — such as telling us that the Moon is shining without mentioning from which direction, or giving the time at which it sets without describing its phase. So we are fortunate that the shape, position, and schedule of the Moon are closely related, allowing us to frequently deduce some of its properties from others. The basic relationships are sketched in the following diagrams for those who might be unfamiliar with them:

Waxing

Crescent Waxing

Gibbous Full Waning

Gibbous Waning

Crescent Already in the western sky at sunset.

Sets before midnight. Still in the eastern sky at sunset.

Passes overhead before midnight.

Sets before dawn. Rises at sunset

Overhead at midnight

Sets at dawn Rises before midnight.

Passes overhead after midnight.

In the western sky at dawn. Rises after midnight.

Still in the eastern sky at dawn.

In case you find the terminology unfamiliar, the Moon is said to be waxing as it grows toward full, waning as it shrinks again afterwards, to be crescent when less than half full, and to be gibbous when more than half.

The Problem New Moon of February, S.R. 1419

There are many nights during the adventure, and indeed entire weeks and months, for which The Lord of the Rings gives no description of the moon. To display its phases, therefore, requires a general schedule or formula that gives the phase whether the text mentions the moon that night or not. Since the new and full moons in the narrative are separated by different lengths of time, much like the slightly irregular schedule of the real Moon, we cannot merely estimate the moon's phase using the average length of the lunar month and have the results match the text. It would therefore be helpful to find a modern schedule of new and full moons matching those in The Lord of the Rings upon which we could base our predictions.

Unfortunately, any attempt to correlate modern Moon phases with those in The Lord of the Rings fails because of the impossibly long interval between the New Moon of February, S.R. 1419 and the full moon that follows on March 8th. As the Company travel down the Anduin after leaving Lórien, we are told on February 22nd that:

At Aragorn's bidding they paddled now for long spells, and the banks went swiftly by. But they saw little of the country, for they journeyed mostly by night and twilight, resting by day, and lying as hidden as the land allowed. In this way the time passed without event until the seventh day.



The weather was still grey and overcast, with wind from the East, but as evening drew into night the sky away westward cleared, and pools of faint light, yellow and pale green, opened under the grey shores of cloud. There the white rind of the new Moon could be seen glimmering in the remote lakes. Sam looked at it and puckered his brows. (II.9)

We can empathize with Sam and his puckered brows! But while Sam himself is confused because he lost track of time amidst the immortal beauty of Lórien, we are confused because this crescent moon simply should not be visible yet.

Each month, the crescent moon first becomes visible one or two days after the moment at which the moon is new — the instant at which it is most completely dark and at the opposite end of its journey from full. But this means that the actual moment of new moon must have arrived more than a dozen hours before Sam saw its crescent above the lakes, putting the new moon far too early when compared with the subsequent full moon:



Phases of the moon for the beginning of S.R. 1419.

Even after making every possible concession, the schedule of moons presented in The Lord of the Rings remains impossible for the modern moon:

Could the date of the above passage be later than February 22nd, S.R. 1419?

The Tale of Years records that the Company departed from Lórien on the 16th, making that the first day of their voyage; the “ seventh day ” on the Anduin must therefore be the 22nd; and this agrees precisely with the fact that the attack on the boats above Sarn Gebir, which the Tale places on the 23rd, is described in the text as being on the “ eighth night ” of the voyage. Even were we to ignore the Tale of Years , the narrative of The Lord of the Rings is continuous from this point to the full moon of March 8th, so we can verify the time elapsed without reference to dates at all.

The records that the Company departed from Lórien on the 16th, making that the first day of their voyage; the “ ” on the Anduin must therefore be the 22nd; and this agrees precisely with the fact that the attack on the boats above Sarn Gebir, which the places on the 23rd, is described in the text as being on the “ ” of the voyage. Even were we to ignore the , the narrative of is continuous from this point to the full moon of March 8th, so we can verify the time elapsed without reference to dates at all. Could the next full moon have fallen earlier than March 8th?

Although Frodo and Sam see the “ full moon ” from Henneth Annûn before dawn on the 8th, we might be tempted to place the actual moment of full moon on the evening of the 7th, and hope that the moon would still have looked full to Frodo and Sam several hours later; but unfortunately we are told explicitly that Pippin sees the moon as merely “ almost at the full ” after sunset on the 7th.

Although Frodo and Sam see the “ ” from Henneth Annûn before dawn on the 8th, we might be tempted to place the actual moment of full moon on the evening of the 7th, and hope that the moon would still have looked full to Frodo and Sam several hours later; but unfortunately we are told explicitly that Pippin sees the moon as merely “ ” after sunset on the 7th. Could the time between this new and full moon have been less than sixteen full days?

The estimate of only sixteen days is drastically generous, and assumes not only that the full moon fell only two hours after midnight on March 8th, but that when Sam on February 22nd saw the crescent moon right after sunset — at around six in the evening — he achieved a stunning naked-eye observation of a moon only sixteen hours old.

Since in modern times the period between new and full moon never exceeds 15 days, 15 hours, any modern schedule will still fall more than nine hours short of the sixteen-day interval required by the text. At least three wild theories can be contrived to try explaining away the impossibility, but all of them fall short:

Was the full moon viewed from a different enough longitude than the new moon to account for this long interval?

This line of inquiry appears promising for a moment: Henneth Annûn lies to the east of the river Anduin; so Frodo and Sam experienced earlier sunrises and sunsets there than while voyaging on the river; so we could place the full moon they observed nearer the new moon of February. But a glance at the distances involved suggests that the difference was probably less than twenty minutes. And then we remember that it is from Rohan — farther west of the River than Frodo and Sam are to its east — that Pippin, in the early evening, sees the moon as not yet full; so bringing longitude into our reckoning will actually require us to move the full moon later , so it still has enough time to become full after Pippin sees it.

This line of inquiry appears promising for a moment: Henneth Annûn lies to the east of the river Anduin; so Frodo and Sam experienced earlier sunrises and sunsets there than while voyaging on the river; so we could place the full moon they observed nearer the new moon of February. But a glance at the distances involved suggests that the difference was probably less than twenty minutes. And then we remember that it is from Rohan — farther of the River than Frodo and Sam are to its east — that Pippin, in the early evening, sees the moon as not yet full; so bringing longitude into our reckoning will actually require us to move the full moon , so it still has enough time to become full after Pippin sees it. But the text doesn’t say that Sam saw the moon in the sky! It only says he saw the Moon “glimmering in the remote lakes” which could have been magic lakes like the Mirrormere, making visible what the eye could not normally see.

This clever maneuver requires us to read the text as meaning that the Moon was only visible in the lakes, but not also in the sky above them. Besides being a forced and contrived reading of the passage, this explanation would seem to founder on two rocks. First, magic lakes in which the New Moon was visible a day early should certainly have elicited more comment than is made in the text. Second, Sam states late the next evening that “ we'd been a week on the way last night, when up pops a New Moon as thin as a nail-paring ”, clearly using the verb “ up pops ” to describe a Moon seen above the horizon.

This clever maneuver requires us to read the text as meaning that the Moon was visible in the lakes, but not also in the sky above them. Besides being a forced and contrived reading of the passage, this explanation would seem to founder on two rocks. First, magic lakes in which the New Moon was visible a day early should certainly have elicited more comment than is made in the text. Second, Sam states late the next evening that “ ”, clearly using the verb “ ” to describe a Moon seen above the horizon. Could the Third Age have been such a geologically ancient era that the lunar month was longer?

We can receive no help from geologic history, for the scientists tell us that in fact the Moon was closer — and thus produced shorter, not longer, periods between its phases — when the Earth was much younger. And explanations of this sort are discouraged by Tolkien himself in the Appendix on the “Shire Calendar” where he states that in the Third Age, “ The year no doubt was of the same length, for long ago as those times are now reckoned in years and lives of men, they were not very remote according to the memory of the Earth. ”

The only remaining option is simply to accept, without the possibility of an internal explanation, that this particular New Moon of the Third Age fell at least one day early, and determine how to include this aberration in a general framework for computing moon phases.

Causes and Consequences

The impossible moon phases of S.R. 1419 are explained very simply if Tolkien was copying his moon phases out of an almanac for a real year, and mistakenly thought that almanacs use the phrase “new moon” in its colloquial English sense, meaning the date on which the new crescent moon appears. But almanacs in fact use “new moon” in its astronomical sense, to mean the moment when the moon is most dark. Through this mistake, Tolkien would have put a crescent moon in his narrative everywhere he really wanted the dark of the moon, and would thus have forced the actual new moons in Middle-earth to each be one or two days too early.

If one examines the very few dates which Tolkien could have counted as the first day of Shire year 1419 and gotten a pattern of full and new moons matching the full and crescent moons given in the narrative, one is immediately struck by the presence of Christmas 1941 in the list of dates:

We know from his Letters that Tolkien was rewriting The Lord of the Rings to correct its moon phases in early 1944, when an almanac or calendar from 1942 would not only have been easy to find, but could plausibly have still been lying about his desk.

that Tolkien was rewriting to correct its moon phases in early 1944, when an almanac or calendar from 1942 would not only have been easy to find, but could plausibly have still been lying about his desk. Tolkien had already displayed a fondness for Christian feasts by having the Company leave Rivendell on December 25th (Christmas in our calendar) and bringing the Ring to its end on March 25th (the traditional date of the first Easter); to have counted a modern Christmas as the beginning of a Shire year would have been quite characteristic.

It is much harder to know whether this is relevant, but let us note in passing that “1941” and “1419” are anagrams.

For reference, the following table demonstrates how counting Christmas 1941 as the first day of Shire year 1419 would have given Tolkien precisely the moons required:

1942 Almanac Date in S.R. 1419 Tolkien describes this moon: January 2nd — Full January 8th As “ full ” January 16th — New January 22nd (not described) February 1st — Full February 8th (not described) February 15th — New February 22nd As the “ white rind ” Sam sees March 3rd — Full March 8th As “ full ” March 16th — New March 21st As a new crescent* *Since on the 24th they see a “ waxing moon ... four nights old ”

To display the phase of the moon for this web site, the real moon phases of 1942 are combined with a correction that moves the moment of each new moon about a day and a half earlier. The effect of this correction upon the waxing and waning half-moons must be different: the waxing half-moon must remain in place so that the moon is still crescent when Frodo sees it on February 29th, but the waning half-moon must happen early for a crescent moon to be seen by Frodo on January 16th. The corrected phase we use is therefore:

Lunar References in the Text

Here are all of the references to the actual appearance of the Moon in The Lord of the Rings (a list which ignores things like references to the Moon in poetry and song). References which create problems when trying to work out a realistic schedule of moon phases are highlighted and marked as “problematic”.