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Celtic Tree Calendar · The extra day, 23 December

23 December, the day outside the tree months

23 December is the one day outside Robert Graves' thirteen months of 28 days: the day left over in his year and a day, between the end of Elder and the start of Birch. It has no tree and no Ogham letter, and it is not the solstice.

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An empty stemline drawn as a dotted upright line with no strokes, for a day with no Ogham letter; beside it the words 23 December, the extra day, after Elder, before Birch, no tree and no letter. 23 December The extra day After Elder, before Birch No tree and no letter Graves' year and a day
The extra day has no letter, so its stemline is empty. Drawn by us, as the month figures are.

Facts

Date
23 December
Day of the year
357 (358 in a leap year)
Between
Elder, which ends on 22 December, and Birch, which begins on 24 December
Tree
None
Ogham letter
None
Source
Graves, The White Goddess (1948): the day left over in "a year and a day", as his followers report it
The solstice
One or two days earlier: 21 or 22 December (UTC) in nearly every year

Meaning

Graves' thirteen months of 28 days make 364 days, so one day of the year is left over, and the lists that follow him put it on 23 December, between the end of Elder and the start of Birch. It is the extra day of his "year and a day". It has no tree and no Ogham letter, and it is not the solstice, which falls one or two days earlier.

Our reading treats it as a threshold: the old year finished and the new one not yet begun, a day for looking back and forward at once and belonging fully to neither. That reading is ours, written in 2026.

Not the solstice

The December solstice falls on 21 or 22 December by Universal Time in 195 of the 201 years from 1900 to 2100: on the 22nd in 78 years of the twentieth century and on the 21st in 82 years of the twenty-first. Only in 1903 did it fall on 23 December. For births in this century, 23 December is usually two days after the solstice. It is day 357 of a common year and day 358 of a leap year, not the last day of anything. Graves placed two of his vowels, A and I, at midwinter, as stations of the year rather than months; we do not compute them.

The mistletoe that was added later

Pagan calendar pages of the 2000s gave this day a sign of its own, the mistletoe, with an Irish-looking name and an Ogham letter. None of it has a source. Mistletoe is in no medieval tree list and has no Ogham letter; its Irish name is drualus; and the letter our old engine drew for the day was Ruis, Elder's own. We dropped the sign in October 2026. Its old page now leads to the system page, and is to lead here.

The mistletoe story itself comes from Pliny. He wrote that the Druids "held nothing more sacred than the mistletoe and the tree that bears it", and that a priest in a white robe cut it with a golden sickle on a set day of the Moon, the sixth in his Latin. He names no solstice and no calendar. The idea that the Druids saw the mistletoe as the soul of the oak is J. G. Frazer's theory, from 1890. Culpeper's herbal of 1652 puts the plant under the Sun as English plant lore, which has nothing to do with this day.

In the other lists

The lists that follow Graves closely keep 23 December apart, as we do. Most tree-sign websites and calculators have no extra day at all and run Elder to 23 December, so a person born on this day is Elder there and has the extra day here. Every other date agrees. The start of the year at midwinter, and so this day at its end, is Graves' choice: the Insular Celtic year turned at Samain and Beltaine.

Correspondences

Each item with how it stands: “sourced” is in the work cited, “our construction” is EsoTerrier’s own, and “disputed” means the sources disagree.

Place in Graves' year
The day left over after thirteen months of 28 days sourced
Relation to the solstice
One or two days after it; usually two days after in this century sourced
The mistletoe sign
A later popular addition with no source, no letter and no Irish name; not used disputed
Mistletoe in Irish
drualus sourced
Our reading
A threshold between the old year and the new, belonging fully to neither our construction

How the schools read it

Graves, 1948
The day left over in his "year and a day", with no tree.
Lists that follow Graves
Keep 23 December as the extra day, apart from the months.
Tree-sign websites
No extra day: Elder runs to 23 December.
Pagan calendar pages of the 2000s
A mistletoe sign with an invented name and letter; no source.
EsoTerrier
Graves' extra day, with no tree and no letter, and our own short reading.

Claims about it

  • 23 December is the winter solstice, or the last day of the solar year.

    false

    What the record shows: The December solstice (UTC) falls on 21 or 22 December in 195 of the 201 years from 1900 to 2100, and on 23 December only in 1903. 23 December is day 357 of a common year and day 358 of a leap year.

  • 23 December is the day of the mistletoe, a sign with its own Irish name and Ogham letter.

    false

    What the record shows: Graves left the day without a tree. Mistletoe is in no medieval tree list and has no Ogham letter; the Irish for it is drualus. The letter our old engine showed for the day was Ruis, Elder's.

  • The Druids cut mistletoe at the winter solstice, or on 23 December.

    false

    What the record shows: The only ancient account, Pliny's, has them cut it from an oak on a day of the Moon, the sixth in his Latin (his Victorian translators print the fifth). No solstice is named.

  • The Druids saw the mistletoe as the soul of the oak.

    unverified

    What the record shows: A theory of J. G. Frazer's, from 1890, not a belief any ancient source records.

  • The Celtic year turned on 23 December.

    false

    What the record shows: The Insular Celtic year turned at Samain, about 1 November, and Beltaine, about 1 May. The day left over at the end of the year is Graves' device.

Elsewhere on EsoTerrier

Sources

Primary texts (4)
  1. Robert Graves, The White Goddess. London: Faber and Faber, 1948 (revised 1952 and 1961). Facts only; not quoted.
  2. Pliny the Elder, Natural History 16.95, tr. John Bostock and H. T. Riley (1855). perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137%3Abook%3D16%3Achapter%3D95
  3. The Unicode Standard, Ogham block U+1680 to U+169F (encoded in Unicode 3.0, 1999). unicode.org/charts/PDF/U1680.pdf
  4. Nicholas Culpeper, The English Physitian (1652), as The Complete Herbal. gutenberg.org/ebooks/49513
Studies and other sources (6)
  1. "Celtic calendar", Wikipedia (orientation only). en.wikipedia.org/wiki/Celtic_calendar
  2. "Ritual of oak and mistletoe", Wikipedia (orientation only). en.wikipedia.org/wiki/Ritual_of_oak_and_mistletoe
  3. Mary Jones, "Celtic Tree Calendar", Jones's Celtic Encyclopedia (2004). maryjones.us/jce/celtictreecalendar.html
  4. whats-your-sign.com, "Celtic Tree Astrology", Wayback Machine capture of 28 February 2008 (cited only as the source of the claim). web.archive.org/web/20080228140902/http://www.whats-your-sign.com/celtic-tree-astrology.html
  5. Foras na Gaeilge, focloir.ie and teanglann.ie (Modern Irish forms). focloir.ie
  6. Jean Meeus, Astronomical Algorithms, 2nd ed., chapter 27 (1998); our solstice table, 1900 to 2100.
Our own research (2)
  1. EsoTerrier, Celtic Tree research and validation, 11 to 13 October 2026.
  2. EsoTerrier calculation engine, the Celtic Tree Calendar service, its texts and its documentation.

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By EsoTerrier. Written with AI assistance from our research and checked against its sources; last revised 19 October 2026. How we write these pages.

First published ; last revised . Corrections: support@esoterrier.com.