Year 13 BC was either a common year starting on Friday, Saturday or Sunday or a leap year starting on Friday or Saturday (link will display the full calendar) of the Julian calendar (the sources differ, see leap year error for further information) and a leap year starting on Wednesday of the Proleptic Julian calendar. At the time, it was known as the Year of the Consulship of Nero and Varus (or, less frequently, year 741 Ab urbe condita). The denomination 13 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.