 Ovid often mentions consulting these calendars, such as his reference at 1.11 to "pictos fastos" and his references to the actual annotation marks of the calendar.The most important of these calendars for Ovid were probably the "Fasti Praenestini", a contemporary calendar constructed and annotated by the grammarian Verrius Flaccus, whose fragments include much ritual material that can be found in Ovid's poem.The concept of putting these calendars into verse however, seems to be a uniquely Ovidian concept.