Coligny calendar

The Coligny calendar is a Gaulish peg calendar or parapegma made in Roman Gaul in the 2nd century, giving a five-year cycle of a lunisolar calendar with intercalary months. It is the most important evidence for the reconstruction of an ancient Celtic calendar. It is written in Latin inscriptional capitals and is in the Gaulish language. The restored tablet contains sixteen vertical columns, with 62 months distributed over five years.

It was found in 1897 in France, in Coligny, Ain (46°23′N 5°21′E, near Lyon), along with the head of a bronze statue of a youthful male figure. It 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. Based on the style of lettering and the accompanying objects, it probably dates to the end of the second century.

A similar calendar found nearby at Villards d’Heria (46°25′N 5°44′E) is preserved in only eight small fragments. It is now preserved in the Musée d’Archéologie du Jura at Lons-le-Saunier.

Reconstruction

The Continental Celtic calendar as reconstructed from the calendars of Coligny and Villards d’Heria was a lunisolar calendar, attempting to synchronize the solar year and the lunar month. The common lunar yearcontained 354 or 355 days.

The calendar year began with Samonios (samon is Gaulish for summer, Lambert p. 112). Le Contel and Verdier (1997) argue for a summer solstice start of the year. Monard (1999) argues for an autumn equinox start (by association with Irish Samhain).

The entry TRINOX SAMO SINDIV “three-nights of Samonios today”) on the 17th of Samonios suggests that, like the Irish festival of Samhain, it lasted for three nights. The phrase *trinoxtion Samonii is comparable to a Gaulish festival mentioned in a 1st-century AD Latin inscription from Limoges, France, which mentions a “10 night festival (*decamnoctiacon) of (Apollo) Grannus” ( POSTVMVS DVNORIGIS F(ILIVS) VERG(OBRETVS) AQVAM MARTIAM DECAMNOCTIACIS GRANNI D S P D)

The solar year was approximated by the insertion of a 13th intercalary month every two and a half years. The additional months were intercalated 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, OXANTIA POC DEDOR TON IN QVIMON, emended to  OXANTIA PO(N)C(E) DEDOR TON IN(ON) QVIMON(IV) “Three hundred eighty and five are given this year through Quimonios” (Quimon- abbreviating the io-stem dative Quimoniu). 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. 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” (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”. There is no indication of any religious or ritual content.

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, while Olmsted suggested 28 days in year 2 and 29 days in year 4.

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:

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 ​³⁷¹⁄₁₀₉₅₆ = 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 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. Omsted (1992) in a similar argument proposes an origin around “850 ± 300 BC”.

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.

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.

Sample month

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.

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, INIS R, 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.

List of months

The names of the twelve months as recorded are 1 samonios, 2 dumannios, 3 rivros, 4 anagantios, 5 ogronios, 6 cutios, 7 giamonios, 8 simiuisonnios, 9 equos, 10 elembivios, 11 edrinios, 12 cantlos. The Celtic year is dived into two parts: the dark half of the year and the light half of the year. The longest day of the year is at the summer solstice in Giamonios. After the summer solstice, the days will continue to get shorter and darker and so Giamonios marks the beginning of the dark half of the year. Samonios contains the winter solstice and also the shortest day of the year after which the days start to get longer and brighter. Samonios marks the beginning of the light half of the year.

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 3 of 5 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 reconstucton of either *Rantaranos or *Bantaranos is based on reading ANTARAN in the fifth line of the 32nd segment. Olmsted (1992) gives a tentative explanation of *Rantaranos as “the count in between”.