Originally, in Alexandria, Rome, and Gaul, Lent consisted of a fast that lasted only one week. We do not know the reasons which, in the third century, caused Rome to determine to prolong the fast for three weeks. But it was certainly the example of the Savior fasting 40 days in the desert that prompted the Fathers of the Council of Nicaea in 325 to prescribe that Lent should comprised of precisely 40 days.