According to Dom Gregory Dix, the basic shape of the Christian liturgy has remained the same "ever since thirteen men met for supper in an upper room at Jerusalem" some two thousand years ago. According to Martin Connell, the same cannot be said for the liturgical year. The Triduum, or three days of Easter, only emerged in the fourth century. So, too, did Christmas. Earlier, Epiphany was the birthday of the Savior. Although a pre-Easter fast of variable length was observed since earliest times, the precise Forty Day span only appeared, once again, in the fourth century. And that...