Year 33 BC was either a common year starting on Saturday, Sunday or Monday or a leap year starting on Sunday (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 Saturday of the Proleptic Julian calendar. At the time, it was known as the Year of the Consulship of Octavian and Tullus (or, less frequently, year 721 Ab urbe condita). The denomination 33 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.