Celtic calendar

The Celtic calendar was a way that ancient Celts used to keep track of time. It helped them decide when days, weeks, months, and seasons began, and when special festivals should happen. One of the best-known examples of a Celtic calendar is called the Coligny calendar. It was made in the 2nd century CE in Roman Gaul, which is now part of France. This calendar gives us important clues about how the Celts understood and organized their world.

Continental Celtic calendar

The Coligny calendar is the oldest known Celtic lunisolar ritual calendar. It was found in Coligny, France, and is now shown in the Palais des Arts Gallo-Roman museum in Lyon. It dates to the end of the second century CE, when the Roman Empire was using the Julian Calendar in Roman Gaul. The calendar was originally one large plate but now exists only in pieces. It is written in the Gaulish language with the Latin alphabet and uses Roman numerals.

The Coligny calendar matches the cycles of the moon and sun. It considers the phases of the moon important, and each month starts with the same moon phase. The calendar uses a special pattern to keep a normal 12-month calendar matching the moon, adding an intercalary month every 2.5 years. It shows a 5-year cycle of 62 lunar months, split into a “bright” and a “dark” fortnight. The notes on the calendar show that months started with the first quarter moon, and a 13th month was added every 2.5 years to keep the moon and sun in sync.

Medieval Irish and Welsh calendars

Further information: Gaelic calendar and Welsh holidays

The ancient Irish and Welsh people divided their year into two parts: a light half and a dark half. They believed the day began at sunset, so the year also started when darkness arrived, at Calan Gaeaf/Samhain (around November 1 in today's calendar). The light half of the year began at Calan Haf/Bealtaine (around May 1).

Julius Caesar wrote in his book Gallic Wars that the Gaulish Celts counted days so that the night came before the day. They measured longer periods in nights, like the English word "fortnight" which means two weeks. The Laws of Hywel Dda often mentioned periods of nine days instead of the eight nights we now call a week.

Native calendar terms in Celtic languages

Many words for months, days, and times used in Celtic languages today came from Latin, showing how Roman culture and Christianity influenced the Celts. For example, the names for January, February, March, and other months are similar in old and modern Celtic languages.

Some Celtic words for time survived even after adopting the Roman calendar. These native terms show that the Celts had their own ways of talking about time before Roman influence.

In Neopaganism

In some Neopagan religions, people use a "Celtic calendar" based on old ways from Medieval Ireland for special ceremonies. Followers of Reconstructionist traditions might celebrate four important Gaelic festivals: Samhain, Imbolc, Beltane, and Lughnasadh.

Some Wiccans mix these festivals with celebrations of the sun's longest and shortest days and the middle points between them, creating what is called the modern Wheel of the Year. A few people also follow ideas from Robert Graves about a "Celtic Tree Calendar," but this idea is not based on real old calendars or ancient Celtic Astrology. It comes from his own thoughts about an old Irish poem.