Coligny calendar

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Overview of the re-assembled tablet found in Coligny, France
Drawing by Seymour de Ricci (1926)[1]

The Coligny calendar is a second century Celtic calender found in 1897 in Coligny, France.[2] It is a lunisolar calendar with a five-year cycle of sixty-two months. It has been used to reconstruct the ancient Celtic calendar. The letters on the calendar are Latin and the language is Gaulish.

The calendar features weeks that consist of five days. Each month has six weeks and either 29 or 30 days. There are twelve such months in a year, or 354 days. A calendar cycle consisted of five years of this type, sixty regular months plus two intercalary months. For the calendar to remain in synch with the lunar phases, the five-year cycle must have been 1,831 days long. This would have made the calendar drift out of synch with the seasons by almost a day every year. Roman sources suggest that the Celtic calendar had a thirty-year cycle. The solar drift issue could have been dealt with by dropping a month once every thirty years.[3]

Each Celtic month started on the sixth day of the lunar cycle, according to Pliny the Elder. This is the date of the quarter moon, the easiest lunar date to confirm by direct observation.[3]

The calendar is now held at the Gallo-Roman Museum of Lyon-Fourvière. It was engraved on a bronze tablet, preserved in 73 fragments, that was originally 1.48 metres (4 ft 10 in) wide by 0.9 metres (2 ft 11 in) tall.[4] Based on the style of lettering and the accompanying objects, it probably dates to the end of the second century.[5][6] A similar calendar found nearby at Villards d'Heria is preserved in only eight small fragments. It is now preserved in the Musée d'Archéologie du Jura at Lons-le-Saunier.

List of months[edit]

The names of the twelve regular months are recorded as Samonios, Dumannios, Rivros, Anagantios, Ogronios, Cutios, Giamonios, Simiuisonnios, Equos, Elembivios, Edrinios, and Cantlos. There were two intercalary months, Quimonios, which appeared in first year of the five year calendar cycle, and Sonnocingos, which appeared in the third year.

Samonios refers to summer (samo-) while Giamonios refers to winter (giamos). The meanings of the other names are less clear. The Celtic year was divided into halves: "summer" from May 1 to October 31, and "winter" from November 1 to April 30.

A five-year cycle would have drifted by nearly a day every year compared to the seasons. So it was probably adjusted somehow. If an intercalary month was dropped every thirty years, the solar and calendar cycles could be brought back into alignment.

Value Name Days Etymology      Interpretation     
I-1 Quimonios 30 Unknown meaning Intercalary for year one
1 Samonios 30 Samo- is Gaulish for summer.[7] Celtic summer started on May 1. There was a three-night festival beginning on 17 Samonios, according to the calendar. May
2 Dumannios 29 Compare to Latin fūmus. Delamarre suggests "month of fumigations."[8] June
3 Riuros 30 Compare to Old Irish remor (stout, thick, fat) and Welsh rhef (thick, stout, great, large). Delamarre suggests "fat month." July
4 Anagantio 29 Delamarre suggests "month of ritual ablutions." The first day of fall was August 1 August
5 Ogronnios 30 Delamarre suggests a month of cold or winter September
6 Cutios 30 Delamarre suggests a month of invocations October
I-2 Sonnocingos 30 March of the sun?[9] Intercalary for year three
7 Giamonios 29 This name is derived from giamos, the Gaulish word for winter.[10] Celtic winter started on November 1. Gam is old Irish for November, according to Cormac's Glossary. So this month can be identified with greater confidence than others on this calendar. November
8 Simivisonnios 30 Simi could mean half, so "half the course of the sun."[11] December
9 Equos 29 or 30 Possibly a month of horses or livestock.[12] January
10 Elembivios 29 Compare to the Celtic word for "deer" and the Attic Έλαφηβολιών "deer-hunting month".[13] The first day of spring was February 1. February
11 Edrinios 30 Compare with Old Irish aed "fire", "heat."[14] March
12 Cantlos 29 Delamarre suggests "month of chanting." April[15]

The names of the twelve regular months can be reconstructed with some certainty in spite of the fragmentary state of the calendar, as each of them was repeated five times. The two intercalary months occur only once each, the first intercalary month happens on year one of five and happens between Cantlos and Samonios and contains 29 days. The second intercalary moon happens on year three of five and contains 30 days between Cutios and Giamonios. The intercalary month names are consequently reconstructed with much less certainty. The name Quimonios is obtained from reading the very end of the first segment as QVIMON.


The Coligny calendar was a lunisolar calendar. It attempted to synchronize the solar year and the lunar month. The common lunar year contained 354 or 355 days.

The first month of the year was Samonios. The name was based on samo-, Gaulish for summer.[7] This suggests that the Celtic year once started on the summer solstice, as argued by Le Contel and Verdier (1997). However, Monard (1999) argues for an autumn equinox start by comparison with Irish Samhain.

Detail of Samonios (year 1), with Quimon- visible at the top.

The entry 17 Samonios refers to "three nights of Samonios."[16] This festival may be equivalent to a ten-night festival of Apollo Grannus recorded in a first-century AD Latin inscription from Limoges.[17][18]

An intercalary month every two and a half years. The additional months were placed before Samonios in the first year, and between Cutios and Giamonios in the third year. The name of the first intercalary month is not known with certainty, the text being fragmentary.

In a suggestion first made by Schmidt (1979:198), the name of the first intercalary month is probably Quimonios, found in the final verse of the gnomic line at the end of the month[19] "Three hundred eighty and five are given this year through Quimonios" (Quimon- abbreviating the io-stem dative Quimoniu).[20]

The name of the second intercalary month is reconstructed as Rantaranos or Bantaranos, based on the reading of the fifth line in the corresponding fragment.

A gnomic verse pertaining to intercalation was taking up the first two lines, read as CIALLOS B(IS) SONNO CINGOS.[21] The term sonno cingos is interpreted as "sun's march" = "a year" by Delamarre (2003).

The months were divided into two halves, the beginning of the second half marked with the term atenoux or "renewal"[22] (cf. Old Irish athnugud "renewal"). The basic unit of the Celtic calendar was thus the fortnight or half-month, as is also suggested in traces in Celtic folklore. The first half was always 15 days, the second half either 14 or 15 days on alternate months (similar to Hindu calendars).

Months of 30 days were marked MAT, months of 29 days were marked ANM(AT). This has been read as "lucky" and "unlucky", respectively, based on comparison with Middle Welsh mad and anfad, but the meaning could here also be merely descriptive, "complete" and "incomplete".[23] There is no indication of any religious or ritual content.[24]

The Coligny calendar as reconstructed consisted of 16 columns and 4 rows, with two intercalary months given half a column (spanning two rows) each, resulting in a table of the 62 months of the five-year cycle, as follows (numbered 1–62, with the first three letters of their reconstructed names given for ease of reference; intercalary months are marked in yellow):


In spite of its fragmentary state, the calendar can be reconstructed with confidence due to its regular composition. An exception is the 9th month Equos, which in years 1 and 5 is a month of 30 days but in spite of this still marked ANM. MacNeill (1928) suggested that Equos in years 2 and 4 may have had only 28 days,[25] while Olmsted suggested 28 days in year 2 and 29 days in year 4.[26]

The following table gives the sequence of months in a five-year cycle, with the suggested length of each month according to Mac Neill and Olmsted:

month name Year 1 Year 2 Year 3 Year 4 Year 5
Quimonios 30
1. Samonios 30 30 30 30 30
2. Dumannios 29 29 29 29 29
3. Riuros 30 30 30 30 30
4. Anagantio 29 29 29 29 29
5. Ogronnios 30 30 30 30 30
6. Qutios 30 30 30 30 30
Rantaranos 30
7. Giamonios 29 29 29 29 29
8. Semiuisonns 30 30 30 30 30
9. Equos 30 28 30 28/29 30
10. Elembiuios 29 29 29 29 29
11. Aedrinios 30 30 30 30 30
12. Cantlos 29 29 29 29 29
year length 385 353 385 353 or 354 355
total length 1831 or 1832 days

The total of 1831 days is very close to the exact value of 62 × 29.530585 = 1830.90 days, keeping the calendar in relatively good agreement with the synodic month (with an error of one day in 50 years), but the aim of reconciling the lunar cycle with the tropical year is only met with poor accuracy, five tropical years corresponding to 5 × 365.24219052 = 1826.21 days (with an error of 4.79 days in five years, or close to one day per year).

As pointed out already by Ricci (1898), based on the mention of a 30-year cycle used by the Celts in Pliny's Naturalis historia (book 16), if one intercalary month is dropped every thirty years, the error is reduced to 30 – (6 × 4,79) = 1.27 days in a 30-year period (or a shift of the seasons by one day in about 20 to 21 years). This proposed omission of the intercalary month once in 30 years also improves the accuracy of the lunar calendar, assuming 371 lunations in 10,956 days, or an assumed synodic month of 37110956 = 29.53010 days, resulting in an error of one day in 195 years.

Steinrücken (2012) has proposed that Pliny's statement that the Celtic month begins on the sixth day of the month[27] may be taken as evidence for the age of this system: assuming that the month was originally aligned with lunations, a shift of five days corresponds to a period of 975 years, suggesting a starting date in the 10th century BC.[28] Omsted (1992) in a similar argument proposes an origin around "850 ± 300 BC".[29]

In the Coligny calendar, there is a hole in the metal sheet for each day, intended for a peg marking the current date. The middle of each month is marked atenoux, interpreted as the term for the night of the full moon.[30]

There is an additional marker prinni loudin in 30-day months (MAT), at the first day of the first month (Samonios), the second day of the second 30-day month, and so on. The same system is used for 29-day months (ANMAT), with a marker prinni laget. In Olmsted's interpretation, prinni is translated "path, course", loudin and laget as "increasing" and "decreasing", respectively, in reference to the yearly path of the Sun, prinni loudin in Samonios marking summer solstice and prinni laget in Giamonios marking winter solstice.[31]

Sample month[edit]

The following table shows the arrangement of a complete month (Samonios of year 2, with TRINVX(TION)SAMO(NII) marked on the 17th day). This is the only month out of 62 that has been preserved without any gaps.[32]

Each month is divided into two half-months or "fortnights" divided by the word atenoux. Within each half-month, the arrangement is tabular, beginning in the first column with the Roman numeral of the day of the half-month (with the hole "◦" for the peg marking the current day indicated as a circle). In the second column are occasional "trigrams" of the form +II, I+I or II+, and sometimes the letter M, of unknown significance. In a third column, each day is marked by the letter N or D (excepting days marked as prinni loudin or prinni laget). In the final column, days are marked with additional information, such as IVOS,[33][34] INIS R,[35] AMB (only found on odd days), among others.

In the month Samonios depicted above, the 17th day is marked TRINVXSAMO, corresponding to TRINOSAM SINDIV in Samonios of year 1.

The name of the following month, DVM(AN), is mentioned several times (on days 1, 3, 8 and 16). Conversely, the following month marks days 1, 8, 16 and 17 with SAMON(I). This "exchanging of days" in odd months with the following, and in even months with the preceding month is also found in other parts of the calendar.


  1. ^ The arrangement by de Ricci misplaces four fragments according to Duval and Pinault (1986).
  2. ^ Lehoux, D. R. Parapegmata: or Astrology, Weather, and Calendars in the Ancient World. PhD Dissertation, University of Toronto, 2000.
  3. ^ a b McKay, Helen T., "The Coligny calendar as a Metonic lunar calendar," Études celtiques, 2016:42, pp. 95-121.
  4. ^ Delamarre, p. 111. Coligny Calendar
  5. ^ Duval, P.M. and Pinault, G., Recueil des inscriptions gauloises, Tome 3: Les Calendriers (Coligny, Villards d'Heria), CNRS, Paris, 1986, pp. 35-37.
  6. ^ Delemarre, Xavier, La langue gauloise, Editions Errance, 2nd edition, Paris, 2003, p.111.
  7. ^ a b Delamarre p. 267
  8. ^ Delemarre, p. 154.
  9. ^ Delamarre, p. 278.
  10. ^ Delamarre, p. 179. "L'étymologie est transparent puisque le nom du mois et fait sur celui de l'hiver giamo-."
  11. ^ Delamarre, p. 274.
  12. ^ Delamarre, p. 165.
  13. ^ Delamarre, pp. 161-162.
  14. ^ Delamarre, p 34.
  15. ^ 15th Cantlos is marked TIOCOBREXT(IO)
  16. ^ TRINOX[tion] SAMO[nii] SINDIV "three-nights of Samonios today."
  18. ^ Lejeune, Michel, "Notes d'etymologie gauloise" ("XI. Les 'Dix Nuits' de Grannos"), Études Celtiques, XXXI, 1995, 91–97.
  20. ^ Olmsted, Garrett, "The Use of Ordinal Numerals on the Gaulish Coligny Calendar", The Journal of Indo-European Studies 16 (1988), p. 296.
  21. ^ Dottin (1920:192); Delamarre p. 116.
  22. ^ The interpretation of atenoux as "returning night" is improbable (Delamarre p.58) and "renewing" would seem more probable; thus the month would start at new moon and atenoux would indicate the renewal, ie the full moon.
  23. ^ Bernhard Maier: Lexikon der keltischen Religion und Kultur. S. 81 f.
  24. ^ Bernhard Maier: Die Religion der Kelten. Götter, Mythen, Weltbild, Stuttgart, 1994, 60f.
  25. ^ Eóin MacNeill: On the Notation and Chronology of the Calendar of Coligny, Eriu X, 1928, 1–67.
  26. ^ Garrett Olmsted: The Gaulish calendar (1992), ISBN 3-7749-2530-5. Garrett Olmsted: A Definitive Reconstructed Text of the Coligny Calendar (2001), ISBN 9780941694780
  27. ^ Pliny, NH 16.95: "The mistletoe, however, is but rarely found upon the oak; and when found, is gathered with rites replete with religious awe. This is done more particularly on the sixth day of the moon, the day which is the beginning of their months and years, as also of their ages, which, with them, are but thirty years. This day they select because the moon, though not yet in the middle of her course, has already considerable power and influence; and they call her by a name which signifies, in their language, the all-healing." Bostock, John, Henry Thomas Riley (eds) (1855). Pliny the Elder, The Natural History Book 16, "the natural history of the forest trees". English translation (available online). Original Latin (also available). The Latin text of the specific passage is est autem id rarum admodum inventu et repertum magna religione petitur et ante omnia sexta luna, quae principia mensum annorumque his facit et saeculi post tricesimum annum, quia iam virium abunde habeat nec sit sui dimidia.
  28. ^ Burkard Steinrücken, Lunisolarkalender und Kalenderzahlen am Beispiel des Kalenders von Coligny (2012), pp. 7, 19.
  29. ^ "Most probably the 30-year calendar developed in a purely preliterate tradition as the displacement of the Irish quarter festivals suggests in projecting an origin around 850 ± 300 BC [...] If so, the calendar must have been preserved from generation to generation by a body of supportive gnomic verse." Olmsted (1992:107).
  30. ^ Garrett Olmsted: The Gaulish calendar, Bonn, 1992, p. 172.
  31. ^ Garrett Olmsted: The Gaulish calendar, Bonn, 1992, pp. 76, 176–177
  32. ^ Dottin (1920). "page 182". La langue gauloise [The Gaulish Language].
  33. ^ Series of days labelled IVOS occur in sequence, marking a period of eight or nine days running from the end of one month to the beginning of the next (mostly 26th to 4th), often interpreted as "festival days", apparently of the nature of a "movable feast" as the IVOS days do not occur in the same months of different years in the five-year cycle. The word ivos has long been associated with the Celtic word for "yew" – Rhys (1910, p. 52), c.f. Ivo, īwaz – but Zavaroni (2007, p. 97) suggests that in this context it means "(con)junction".
  34. ^ Stern, Sacha (2012). Calendars in Antiquity. Oxford University Press. p. 305. ISBN 9780199589449. At the beginning of Elembiv in year 2 there are five IVOS days, whereas other months begin with only three or four. The unusually long run at the beginning of Elembiv in year 2 appears to be making up for a lost IVOS day at the end of Equos.
  35. ^ INIS R always follows N in the preceding column. Annuaire. Librairie Droz. École Pratique des Hautes Études. 1966–1967. p. 220. ISBN 9782600053280.


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