In 1897, a
fragmented bronze calendar was discovered in
Coligny, France. It is believed to date from
around 50 BC, and appears to be the remains
of a Romanized Gaulish model of a Celtic
lunar and solar calendar.
It displays a
cycle of approximately five years on 62
tables. Unlike our present-day calendar which
dates back to Julius Caesar, this system used
the accurate period of the moon's orbit
around the Earth (the lunar month) to measure
the passage of time. Each lunar month
corresponds to 29.53 days. In this Gaulish
model, the month was divided into two 15-day
periods.
A solar year,
the time taken by the Earth to circle the
sun, or one revolution of the sun about the
Vernal Equinox, is nominally 365 days. Twelve
revolutions of the moon, however, equals only
354 days. It was therefore necessary with the
Coligny calendar to make two adjustments:
first, using alternate months consisting of
29 and 30 days; second, adding a month every
2 1/2 or 3 years to link up the shorter lunar
year of 354 days to the solar year of 365
days.
In Celtic
legend the new year started on the moonrise
of the first last-quarter moon after the
autumnal equinox. In the Celtic regions of
Britain and Ireland, the tradition was held
that the new year started at Samhain
(November 1) so that it would always occur on
the same day of the solar cycle. A different
calendar system from the one found in Gaul,
one that reconciled the lunar and solar
yearly cycles, was then in use . The year
consisted of 13 months, 12 of them roughly
equivalent to our modern calendar, with the
inclusion of a short, three-day month at the
end of October leading up to the new year. It
is in this arrangement of months that Celtic
cosmology and Druid philosophy are linked
through the Ogham alphabet with its 13 calendar
trees.