The Coligny Calendar is a series of stone tablets dating to the time of
Julius Caesar; it is a record of the Gaulic (and thus Celtic) year, though it shows some Roman influence, as
Roman numerals are used. However, the names of the month are given in
Gaulic, and the year begins in
November, keeping with what we know of the
Celtic year. The calendar is both a
lunar and
solar calendar, which causes some problem with drifting, but this was accounted for by their
astronomers (yes, the
Druids). The calendar uses a mathematical arrangement to keep a normal 12 month calendar in sync with the moon by adding an extra month every 2 1/2 years.
Us Gaulic Meaning Designation Length
November Samonios "Summer's End" MAT 30
December Dumannios "Dark Month" ANM 29
January Riuros "Frost Time" MAT 30
February Anagantios "Indoors" ANM 29
March Ogronios "Cold" MAT 30
April Cutios "Windy" MAT 30
May Giamonios "Winter's End" ANM 29
June Simivisonnos "Semi-Spring" or Midsummer MAT 30
July Equos "Horse Month" ANM 29
August Elembivios "Many Fences" ANM 29
September Edrinios "Hot Time" MAT 30
October Cantlos "Song" ANM 29
Ciallos (intercalculatory month) MAT 30
ANM meaning "Bad" and MAT meaning "Good"; notice the good months are all 30 days, and the bad months 29. Also notice that February has been considered bad and short for over 2000 years. BTW: Samonios is of course the same as the Irish "Samhain"
Now, according to The Gallic Wars: "All the Gauls assert that they are descended from the god Dis, and say that this tradition has been handed down by the Druids. For that reason they compute the divisions of every season, not by the number of days, but of nights; they keep birthdays and the beginnings of months and years in such an order that the day follows the night."
And, in reading Pliny's statements on the Druids supposed custom of cutting the mistletoe on the sixth day of the moon, it has been assumed that the month began on the new moon, like the Jewish calendar. Actually, it has a lot of similarities to the Jewish calendar, which leads to an interesting question--did the Celts have contact with the Jews before they migrated west?
According to Ray White, "the era of the New Coligny Calendar (NCC) {began} on October 8th, 1999. This date was chosen because this date corresponds with a new moon on the date of the beginning of European winter. (when the sun is at 15Deg Scorpio)" which is also the day that the megalith at Tara marks the beginning of winter--the day the sun is at 15º Scorpio.
Sources:
Jean Markale: The Pagan Mysteries of Halloween
Ray White's Coligny Calendar page: http://technovate.org/web/coligny.htm