What is "yennayer"

Yennayer is the first day of the agrarian year used since antiquity by Berber people in North Africa. It corresponds to the first day of January of the Julian Calendar, which is shifted thirteen days compared to the Gregorian calendar, i.e. 14 January of every year. Probably due to a mistake of the first cultural associations asking to return to this traditional celebration, the opinion that the traditional date is 12 January is very widespread, especially in Algeria.