^Ó hÓgáin, Dáithí. Myth Legend and Romance: An Encyclopaedia of the Irish Folk Tradition. Prentice Hall Press, 1991. p. 402. Quote: "The basic Irish division of the year was into two parts, the summer half beginning at Bealtaine (May 1st) and the winter half at Samhain (November 1st) ... The festivals properly began at sunset on the day before the actual date, evincing the Celtic tendency to regard the night as preceding the day".