The Celts understood time completely differently than we do. Time was circular, rather than linear. Like the modern Jewish calendar, they reckoned days from sunset to sunset, rather than from dawn to midnight like we do. So in their world, an important feast day would begin at an hour we would today consider the night before. Are you confused yet? This is why I’ve chosen to take artistic licence in my books and count days as we do in the modern world, beginning each day at dawn. Anything else, although technically more accurate, would be too confusing for the reader (and for me!)
Another way the Celts’ sense of time differed from ours was in their calendar. The year was divided into the the dark half of the year (approximately October 31 through April 30) when night was dominant, and the light half of the year (approximately May 1 through October 30) when the sun’s light was at its strongest. They counted 13 lunar months, whereas our Gregorian calendar (adopted in 1582) counts 12 months. Each month began with the full moon and ended right before the next one, whereas if we in the modern world think of the moon at all, the new moon is associated with beginnings, the full moon with the apex of energy and the dark moon with the end of the lunar cycle. In the Celtic calendar, each full moon had its own name/theme based on the agricultural goings on at the time (plow/seed moon, harvest moon, snow moon, etc.) This system worked well until after the feast of Samhain, when there was a period of five days between the festival and the calendrical start of the new year. This was a “time outside of time,” much like our modern leap day, only it held great spiritual significance because it was a time when anything could happen because none of the normal rules applied. Some also say the Celtic zodiac also associated each lunar month with one of 13 sacred trees, but others argue this originated in fiction, but was adopted by modern neopagans as fact.
The seasons were also different for the Celts than we now think of them. Spring began in February, summer in May, autumn in August and winter in October. The Celts, being an agrarian people, divided their year into four great festivals: