Why Lent Is Kept for Different Numbers of Weeks

Further, as for what you say, that in some countries Lent is kept in different ways, for six weeks or for seven: it is one and the same system and manner of fasting that is kept under the different observance of the weeks. For those who think one ought to fast on Saturday too have settled on keeping six weeks. So they fast six days out of the seven, and this, repeated six times, makes up the thirty-six days. It is therefore, as I said, one system and the same manner of fasting, though there seems to be a difference in the number of weeks.