The Coligny Calendar


Today’s date in the New Coligny Calendar is


The Coligny Calendar, or Gaulish Calendar, was a lunisolar calendar which was used in Gaul in the latter part of the B.C.E. period and, possibly, into the beginning of the C.E. period. It used a five-year cycle with intercalary months in order to keep it in synchronisation with the solar year.

The workings of this calendar were preserved in a bronze tablet that was discovered buried near Coligny in France in 1897. It is thought that the tablet itself dates from towards the end of the 2nd century.

It is assumed that the tablet was buried because use of the calendar was banned by the Romans as an indication of druidic practices and, more importantly, flouted the rule that the Julian calendar should be the official calendar in all parts of the Roman Empire.

The workings of this calendar were preserved in a bronze tablet that was discovered buried near Coligny in France in 1897. It is thought that the tablet itself dates from towards the end of the 2nd century. It is assumed that the tablet was buried because use of the calendar was banned by the Romans as an indication of druidic practices and, more importantly, flouted the rule that the Julian calendar should be the official calendar in all parts of the Roman Empire.

A section of the tablet is shown in the image on the right. The holes on the left-hand side of the image are where a peg would have been inserted to indicate the current date in the calendar.

How the Calendar Worked

The calendar had 12 months of 29 or 30 days, giving a common year of 354 days. Every two and a half years a 13th “intercalary” month was inserted to keep the calendar in approximation with the solar year. These were inserted before the 1st month (Samonios) and between the 6th and 7th months (Cutios and Giamonios) in the 3rd year of each five-year cycle. It is not known for sure what these extra months were called, but it is thought that the first intercalary month was called Quimonios and the second one Rantaranos or Bantaranos, based on remains of verses in the recovered fragments of the tablet.

The months were divided into two halves and the beginning of the second half was marked with the term ATENOUX or “renewal”. For this reason some scholars suggest that the month started at full moon and therefore the start of the second half of the month was at new moon, hence the “renewal”, but it is not known for sure.

The months were either 30 days long and marked MAT, or 29 days long and marked ANMAT. We are not sure what these mean but it is thought that they simply mean “complete” and “incomplete”.

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 (the intercalary months are marked “CIALLOS” in the table):

The structure of the calendar has been reconstructed with a reasonable level of confidence due to the regular composition of the tablet, apart from the 9th month Equos, which seems to have varied between 28, 29 and 30 days depending on the year of the cycle.

The following table shows the sequence of months in the five-year period, with the suggested length of each month shown.

Month Name
Year 1
Year 2
Year 3
Year 4
Year 5
Quimonios
30
1. Samonios
30
30
30
30
30
2. Dumannos
29
29
29
29
29
3. Rivros
30
30
30
30
30
4. Anagantios
29
29
29
29
29
5. Ogronios
30
30
30
30
30
6. Cutios
30
30
30
30
30
Rantaranos
30
7. Giamonios
29
29
29
29
29
8. Semivisonna
30
30
30
30
30
9. Equos
30
28
30
28/29
30
10. Elembivos
29
29
29
29
29
11. Edrinios
30
30
30
30
30
12. Cantlos
29
29
29
29
29
Year Length
384
353
385
353/354
355
Total Length
1,831 or 1,832 days

The total length of 1,831 days is very close to the exact value of 62 × 29.530585 = 1,830.90 days, keeping the calendar in relatively good agreement with the synodic month (with an error of one day in 50 years). It may be that an extra day was added periodically to compensate for this.

The aim of reconciling the lunar cycle with the tropical year is only met with poor accuracy, however, five tropical years corresponding to 5 × 365.24219052 = 1,826.21 days (with an error of 4.79 days in five years, or close to one day per year). Again, other adjustments may have been made to compensate for this discrepancy, but this is not clear from the remains of the tablet.

My Reconstruction

My reconstruction of the calendar has been adjusted to try to provide a more accurate system. In this version there are 6 months of 30 days and 6 months of 29 days in a standard year. Therefore, Equos always has 29 days, except in the fifth year of the cycle when an extra day is added for adjustment purposes. Additionally, in every sixth cycle the extra month of Rantaranos is omitted. This is the system used to calculate the date that appears at the top of this page.

There is also debate about when the calendar began each year. Samonios could be cognate with samon, 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). I have chosen the latter option as this ties in with my New Celtic Calendar.

I decided to begin the modern epoch of this conjectural calendar on 9th October 1999. This date was chosen because it “corresponds with a new moon on the date of the beginning of European winter. (when the sun is at 15 Deg Scorpio).“. This would have been closer to the 7th November, however, but remember that in the first year the extra month Quimonios is added at the beginning, and as there was a new moon on 9th October 1999 this is the start date chosen for the modern calendar. According to my information, however, the new moon in October 1999 actually took place on 9th October, so this marks the beginning of year NCC 1 in the New Coligny Calendar.