Year 1 BC was a common 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 Thursday of the Proleptic Julian calendar. It is also a leap year starting on Saturday, in the Proleptic Gregorian calendar. At the time, it was known as the Year of the Consulship of Lentulus and Piso (or, less frequently, year 753 Ab urbe condita). The denomination 1 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. The following year is 1 AD in the widely used Julian calendar, which does not have a "year zero".