Pope Gregory I (590-604) established the tradition of Ash Wednesday.
This included the marking of parishioners' foreheads with ashes in the shape of a cross.
The Lenten observations of fasting and prayer did not always take place for 40 consecutive days.
In Jerusalem, fasting was observed for 40 days, Monday through Friday, but not on Saturday and Sunday.
Thus, Lent lasted for a total of eight weeks.