The Celtic tree calendar, also called the Beth-Luis-Nion Calendar, is a modern calendar based on modern, theoretical interpretations of the Ogham alphabet, or the Celtic Tree Alphabet. While there is no evidence of ancient Celts or Druids using a calendar that even resembled this one, it has, however, become a valuable spiritual, liturgical and magical tool for some modern NeoPagans who identify with the ancient Celts. Celtic Reconstructionist Pagans reject it utterly as a complete fabrication with no historic basis. Which of course it is. Others embrace it as a tool to enhance their magic, their spirituality and their connection with nature and to help give structure to their rituals.
A Celtic tree calendar was first posited in the 19th century by Edward Davies based on research of the Ogygia and the Book of Ballymote further developed by Robert Graves in his book The White Goddess and further developed by Ross Nichols.
The calendar has 13 months of 28 days and an extra day posited as the “year and a day” day. It begins with the winter solstice, in contrast to the tradition of Samhain as the Celtic New Year.
Graves’ Celtic Tree Calendar
Beth (Birch) December 24th to January 20th
Luis (Rowan) January 21 to February 17
Nion (Ash) February 18 to March 17
Fearn (Alder) March 18 to April 14
Saille (Willow) April 15 to May 12
Uath (Hawthorn) May 13 to June 9
Duir (Oak) June 10 to July 7
Tinne (Holly) July 8 to August 4
Coll (Hazel) August 5 to September 1
Muin (Vine) September 2 to September 29
Gort (Ivy) September 30 to October 27
Ngetal (Reed) October 28 to November 24
Ruis (Elder) November 25 to December 22
December 23 Extra day for “Year and a Day”
Variations on the Calendar
Due to its obvious limitations, the calendar has been changed a little here and there to fit with various traditions. Some have altered the start dates of the month to begin on the new moon or the full moon make the calendar more in line with lunar tradition and many believe the calendar should have been started at Samhain, which is regarded as the traditional Celtic New Year.
A simpler variation based on the Gregorian calendar makes it much easier to keep track of though it has many problems. As many believe the calendar should begin on November 1st to correspond with Samhain as the Celtic or Witches New Year, this variation would assign Beth to November, Luis to December and so on. However, this leaves the problem of what to do with the extra month. One solution is to declare Ruis an extra month for leap years.
Lunar Variation, beginning at Samhain
This variation begins with Beth at Samhain and ending on the first new moon (or full moon) after Samhain. It is true that this could result in Beth lasting only a day, but it follows with the tradition of lunar days. The new moon starts the first lunar day and the next moonrise starts the second lunar day, the first may last only a few minutes. This also solves the problem of extra moons and extra days. The extra “Year and a Day” day posited by Graves would occur on Samhain eve.
Full Moon Names
Much more widely accepted than the calendar is naming the full moons based upon it. If you follow Graves’ model of beginning with the winter solstice, the first full moon after the winter solstice would be the Birch moon, etc. More popular, however, is the Samhain as New Year model, in which case the first full moon after Samhain, November, is the Birch moon. The next in November/December is the Rowan Moon, then the Ash Moon in December/January, the Alder Moon in January/February, the Willow Moon in February/March, the Hawthorn Moon in March/April, the Oak moon in April/May, the Holly Moon in June/July, the Hazel moon in July/August, the Vine moon in August/September, the Ivy moon in September/October, the reed moon in October and the Elder moon, the 13th moon when needed.
Celtic Tree Astrology
In The White Goddess, Grave suggested a system of astrology that went along with this calendar. This idea has been further developed in modern times.