In the modern calendar a year has 12 solar months. In the Celtic calendar a year has 13 lunar months. The decision to create lunar or solar years affects the number of days in a year. For instance 13 (lunar months) x 28 (days) = 364 days; 12 (solar months) x 30 (days) = 360 days. 360 + 5 using 70ths which Thoth won from Selene In the Celtic tradition the year is divided into two: a dark half: Giiemorotlio: Cycle of sprouts: Long Nights + Short Days a light half: Semorotlio: Cycle of seeds: Long Days + Short Nights