This page was created by Marc Carlson
It was last edited 9 June 2004

Moon Phases
The phases of the moon listed are derived from Pliny the Elder, Natural History XVI xcv. 250

est autem id rarum admodem inventu et repertum magna religion pettitur et ante omnia sexta luna (quae principia mensum annorumque his facit) et seculi post tricesimum annum, quia iam viium abunde habeat nec sit sui dimidia...

Mistletoe is, however, seldom found on a hard-oak, and when it is discovered it is gathered with great ceremony, and particularly on the 6th day of the moon (which for those tribes constitutes the beginning of the months and the years) and after every thirty years of a generation, because it is then rising in strength and not one half its full size.
So, if we assume that the new moon is the 1st day of the month, then seven days later the moon is in its first quarter.  Approximately seven days later, it will be full, and so on.  Each stage appears to be three days in length.  However, by shifting the beginning of the month forward by six days, the First Quarter will appear on the 1st, the Full Moon on the 7th 8th & 9th, the third Quarter about 14th, 15th, and 1st.  The New Moon will then appear (in theory) about the 7th or 8th of the second half of the month.

Olmsted, Garrett. The Gaulish Calendar, A reconstruction from the bronze fragments from Coligny with an analysis of its function as a highly accurate lunar/solar predictor as well as an explanation of its terminology and development. Bonn: Dr. Rudolf Habelt GMBH, 1992.