In a commentary I read, "Honoring of seasons and cycles of the year was part of Celtic religion." A reference was given to "Historia religionum; handbook for the history of religions. Edited by C. Jouco Bleeker and Geo Widengren." (The comment is on Paul's statement to the Galatians that "You observe days and months and seasons and years.") I have read different sources on the Celtic religious practices in order to find something about their observances of seasons etc. but have not really come across anything. Therefore, it was with happy anticipation that I borrowed and read the pertinent chapter of "Historia religionum" only to be disappointd in that I found no reference to such observances.
To the question: Can anybody point me to a source that may discuss this topic especially one that you know contains the specific info that I am looking for.