Some historical errors present are most likely part of the literary artifice, whose contextualization is documented in the pages of the book preceding the Prologue, in which the author states that the manuscript on which the current Italian translation was later carried out contained interpolations due to different authors from the Middle Ages to the Modern Era.[40] Eco also personally reported some errors and anachronisms present in various editions of the novel until the revision of 2011:
- The novel mentions bell peppers, first in a recipe ("sheep meat with raw pepper sauce"), then in a dream of Adso, but it is an "impossible dish". These peppers were in fact imported from the Americas over a century and a half after the time in which the novel takes place. The same error is repeated later when Adso dreams of a reworking of the Coena Cypriani, in which among the different foods that guests bring to the table appear, in fact, also the peppers.[41]
- During the seventh day-night, Jorge tells Guglielmo that Francis of Assisi "imitated with a piece of wood the movements of the player violin", an instrument that did not exist before the 16th century.[41]
- At one point in the novel Adso claims to have done something in "a few seconds" when that time measure was not yet used in the Middle Ages.[41]
Moreover, still present in the Note before the Prologue, in which Eco tries to place the liturgical and canonical hours:
If it is assumed, as logical, that Eco referred to the local mean time, the estimate of the beginning of the hour before dawn and the beginning of Vespers (sunset), so those in the final lines ("dawn and sunset around 7.30 and 4.40 in the afternoon"), giving a duration from dawn to noon equal to or less than that from noon to dusk, is the opposite of what happens at the end of November (it is an incorrect application of the Equation of time).
