Bill Vallicella defines epochism
as "the arbitrary denigration of entire historical epochs," and quotes Hegel's slanders against the medieval epoch. Here is what Owen Barfield, History in English Words
(London: Faber, 1953), p. 164, has to say on the topic:
Possibly the Middle Ages would have been equally bewildered at the facility with which twentieth-century minds are brought to believe that, intellectually, humanity languished for countless generations in the most childish errors on all sorts of crucial subjects, until it was redeemed by some simple scientific dictum of the last century.