The Coligny Calendar

The Coligny calendar was discovered in Coligny, France (near Lyon) as little more than a pile of bronze fragments in 1897 – most likely smashed by Roman authorities during the suppression of druidic practice – and painstakingly restored piece by piece. It was originally the size of a rather cramped doorway. Less than half of the calendar remains, but there is enough to clearly see a beautiful time-keeping system that aligned the sun and moon into a single calendar, and listed dozens of holidays, rituals, celebrations, and the like.

There are lots of disagreements about the calendar. For example, although everyone agrees that it effectively tracks both the sun and the moon, it’s uncertain whether months began at the new moon, the full moon, or perhaps the first quarter. In this article, I’m going to state as fact many things that are in contention, because filling the article with equivocations would turn it into a scholarly work, not a philosophical one. For example: I’m going to say that the months begin on the new moon, because in my opinion, that squares best with the evidence.

How It Works

The basic year is quite simple, with twelve months of either 30 or 29 days each. Each month is divided into two parts — a fifteen-day first section, and a second section with fourteen or fifteen days. The month begins and ends with the new moon, and thus the center of the month is the night of full moon.

These are the twelve months, starting with the first month, which is in the fall:

  1. Samonos. “Seeding”. 30 days. The Gaulish equivalent of Samhain. The New Year is thus right around Halloween. The full moon of this month appears in Taurus, the great Bull. Thus in 2008, Samonos began on Oct. 28, and ran until Nov. 27. (However, the Coligny calendar seems to indicate that the Samhain festival was celebrated on the day after the full moon, i.e. Samonos 16th, which would have been Nov. 13 in 2008.)
  2. Dumanos. “Silence”. 29 days. The full moon of this month is in the Great Wheel (Gemini). In 2008, from Nov. 28 to Dec. 26.
  3. Riuros. “Royal Burning.” 30 days. The full moon of this month is in Esus (Cancer). Dec. 27 2008 to Jan. 25, 2009.
  4. Anagantios. “House of the Eaten One.” 29 days. Full moon in the Defeated Lion (Leo); Jan 26 – Feb 23, 2009.
  5. Ogronos. “Keenly Runs”. 30 days. Full moon in Running Lion (Virgo); Feb 24 – March 25, 2009.
  6. Cutios. “House of the Hound.” 30 days. Full moon in Hound (Libra); March 26 – Apr 24, 2009.
  7. Giamonos. “Sprouting.” 29 days. Full moon in Cernunnos (Ophiuchus / Scorpio); Apr 25 – May 23, 2009.
  8. Simivisonna. “Like Birdsong.” 30 days. Full moon in Sky Horseman (Sagittarius); May 24 – June 22, 2009.
  9. Equos. “Dampening”. 29 days. Full moon in Sacrificial Vessel (Capricorn); June 23 – July 21, 2009.
  10. Elembivos. “Evocation of the Stag.” 29 days. Full moon in Smertrius (Aquarius); July 22 – Aug 19, 2009.
  11. Edrinos. “Causes to Run.” 30 days. Full moon in Chariot (Pisces); Aug 20 – Sept. 18, 2009.
  12. Cantlos. “Tail of the Dog.” 29 days. Full moon in Dog’s Tail (Aries); Sept 19 – Oct 17, 2009.

Notice that the New Year in 2009 will occur on Oct 18 instead of 2008’s Oct 28. The calendar is still aligned with the moon, but has drifted from the sun by ten days. After another year, it will have drifted from the sun by another ten days…

This drifting is why the Coligny calendar includes a “leap month” every two and a half years. The leap months are called “Ciallos Buis”, the “Gathering”, and may have marked a time in which people gathered for trade, ritual, and other observances. One Ciallos Buis occurs before the first month of the year (around Samhain), and the other occurs before the seventh month of the year (around Beltane).

One more wrinkle: the month Equos usually only had 29 days, but was given an extra “leap day” every 4th year.

If you want to use the Coligny calendar today, you have to choose which years you’re going to have your leap months. One way (suggested by, and at least as convenient as anything else) is to mark Year 1 as matching roughly with 2000 AD. In this case, the first leap month would occur in the fall of 1999. The last one would have been in the spring of 2007, and the next one will be in the fall of 2009.

Comparing Calendars

Is this system better than the one we have?

Well, having extra months pop up every few years would seem to be disruptive, especially in the modern world, in which stock prices rise and fall depending on whether a company’s earnings are reasonable compared to what it was doing the year before. What if last year was 13 months long instead of 12? How do you compare them fairly? Especially if the 13th month is a big party! Imagine business analysts saying things like, “Retail sales at this year’s Samhain Caillos Buis outperformed 2004, but fell short of the Beltane Caillos Buis of 2007, leading to a disappointing earnings report…”!

Also, I honestly don’t know how well it would work for farmers. It wasn’t necessarily used for agriculture 2000 years ago; the Coligny calendar may have been especially made for ritual, rather than planting. Notably, while the calendar marks dozens of religious observances, and some of its calendar names suggest seasonal changes, nowhere does it get specific about when one ought to plant rutabagas. And unlike our modern calendar, the solar equinoxes and solstices do not happen on anything like the same days from year to year — although they do repeat on a five-year pattern.

Missing also from the calendar is the notion of a seven-day week. Each month was divided roughly into two fortnights, and presumably this was kind of like a “week”, but that’s an awfully long week. And there are no weekends.

On the other hand, you always know where the moon will be, and what phase it’s in, just by knowing the day of the month. For many of us, that’s extremely important. Our system of seven-day weeks was probably originally designed to keep track of where the moon was (one week for each of the moon’s four main phases), but it drifts pretty badly and no one adjusts it anymore. Plus, the Coligny calendar even has a big bonus for Christians!  It makes it much easier to know when Easter (Eostre) will be: either Cutios 18th or Giamonos 18th, depending on which year of the five-year cycle it is.

And frankly, the extra odd months would add some nice variety.  And they’re timed pretty nicely for a number of things, like elections, the Olympics (it’s perfectly set up for that, down to the Winter / Summer Games distinction), college and high school terms, and the like.

Of course, the very best advantage would be the combination of Halloween and New Year’s Day. Now THAT would be a party!


17 responses to “The Coligny Calendar”

  1. Cool article, Jeff! I was aware of the Coligny Calendar but didn’t know much about it before, so I was really interested to learn about it. It does seem like it would be pretty useless for farming if it drifts ten days every non-leap year.

    It’s too bad that Technovate page only has a Windows version of the calendar (well, too bad for me and my Mac, anyway). I’d buy a paper calendar, if only for the novelty.


  2. Great article. I am fascinated by natural measurements. I will definitely give this some research time!


  3. Clare, Thanks! It was fun to research and write. Would you really buy a paper calendar? I could probably make one and make it available through without too much effort. 🙂

    Ken — thanks! Enjoy your research!


  4. Since you translated most (but not all) of the Gaulish words you cited from the Coligny Calendar, I wonder what “Smertrios” means. (Does it translate the same as “Aquarius” — water-bearer — or does it translate as something else, or do we simply not know?)


  5. Kate, the best I can do for “Smertrios” is point you to the Wikipedia article. He is a Gaulish god that the Romans seem to have equated with Mars, and some scholars suggest a link with Hercules, but his name seems to mean “Provider”, so that doesn’t match up particularly. Clouter, however, equates him with “water bearer” Aquarius, and if you assume that what The Provider is providing is water, then you have a nice match. If Clouter is correct (see the Druid Zodiac article), the Smertrios constellation is a figure dipping someone or something into a vat (Capricorn) — or perhaps drawing something out? Most mysterious. 🙂


  6. Jeff…. awesome article. It helped me understand one of my favorite albums entitled “Evocation” with a song titled “Elembivos” which seems to honor the stag god (most likely Cernunos). Also, it helped me to understand the Gauls a bit more. Thanx!


  7. […] to perhaps 100 BC, which may well show a stylized version of the Druidic Zodiac. And we have the Coligny Calendar, from perhaps 200 AD: a calendar of 60 months, which lined up the Moon and Sun in a five-year cycle […]


  8. Hi Jeff, Great article. but I have one question — what are the phrases you have listed next to the names of the months? (ie. seeding, house of the eaten one..etc. I can’t find any other information relating to the months and what those phrases are.



  9. Nick — Honestly I do not remember now where I got those translations. I certainly did not make them up, and I don’t know enough of Latin or Gaulish to try my own translations. But I am kicking myself for not providing a reference. I may have gotten them from the Lost Zodiac of the Druids by Gregory Clouter — I don’t have the book with me right now to double check. But I’d recommend the Wikipedia article for some interesting scholarly speculations.


  10. My birthday is May 6th 1983. I’m not sure of the time. I think it was around 7 am.


    1. Betty, if you were born in the United States or Europe, the moon was probably in Aquarius when you were born, which would make your ‘druid sign’ Smertrius, the Provider.


  11. Hi, i’m making a website about all kinds of old religions and find this article very usefull foor my celtic pages. But I think there is a little mistake in your counting about the leap month. You say that the month would appear before the sixth month around Beltane. I guess these two don’t match up, if the leap month would appear around Beltane, it would be after the sixth month and before the seventh, no?
    Anyway, A lovely calender interpretation non the less 🙂


    1. Saar, you’re absolutely right! Thanks for the correction. I’ve edited the article.


  12. Hi, I’m writing a book set in 388AD with Roman and Brythonic characters. Well, sort of characters… They’re based on real people. But I’m trying to understand the Coligny calendar in order to get the dates right (it seems like the best source for a Celtic thought pattern as regards dates), and I was wondering if you could help… If the first date in the book is 18th September 388AD, would that always be Edrinos? Or do I need to know the dates of new and full moons in 388AD in order to calculate the month…? And do I need to assume when the person / community might have started calculating years, because the calendar ran in cycles before adding extra months or days? Sorry! All the questions!


    1. Hey there! The book sounds fascinating! It’s been a long time since I looked at this carefully, but I believe unfortunately the answer is that you’d need to (a) know which year of the 5-year cycle they were on, and (b) know the dates of the moons in 388. (b) is pretty easy to get (I can get them for you) but (a) is completely unknown, as far as I’m aware. The good part about that, though, is that it gives you authorial discretion… you can pick the year you like.

      I’d be happy to send you the dates of the moons, and also tell you exactly which dates you’re working with, depending on which of the five years of the cycle you’re on. (In other words, you’ll have five dates to choose from.) It will be a few days before I have a chance to get to that, though — are you on a tight schedule?

      (I’ll also note as an aside that I offer a linguistics / languages consulting service to authors. I assisted Sharon Fisher with her upcoming book, The Absinthe Earl (, which is being released in October, and its sequel. By trade I’m a computational linguist and I specialize in linguistic theory, lexicography, machine learning, and the Germanic and Celtic languages. For authorial consulting, I’m just getting started, and my rates are very negotiable 🙂 )


      1. Ah! I was afraid of that! I found the dates of the moons, but in terms of where the year would fall in the cycle I suppose you’re right and I’ll just have to guess! Plus, if I’m understanding this correctly (which I may very well not be, in all honesty)… you’d need to know what year they started counting from? Am I making that up..? Ah, a computational linguist may be very useful actually… I do have a bunch of questions along those lines as well 😂 and I’ll definitely need a consultant for various things, including sense checking, at various points… would you be able to drop me an email? (actual name haha you can see how I got started on this project…)


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