Bearnard Ó Muireagáin suggests that the day called "Trinus Samoni" in the calendar of Coligny is cognate of the Old Irish "Trenae Samna", an alternative name for Samain
The 1 800 years old Gaulish calendar from Coligny, France, is the oldest known Celtic solar-lunar ritual calendar.
It registers a five-year cycle of 62 lunar months, divided into a "bright" and a "dark" fortnight (or half a moon cycle) each.