We will present in this essay three themes for reflection: first, the eminently religious character of ideology in medieval Christendom; second. the role of the "Gregorian Reformation" of the 11th century in the restructuring of this new Christendom; and last, the particular reaction created by the "Gregorian reformers" with temporality (meant as anthropological category). We believe that between myth and utopia, the "Gregorian reformers" tried to create, sometimes without being successful, a border between official and apocalyptic or millenarian eschatology, intending to promote order in society/Christendom.