46 BC 46 BC Year 46 BC was the last year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Caesar and Lepidus (or, less frequently, year 708 "Ab urbe condita"). The denomination 46 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. This year marks the change from the pre-Julian Roman calendar to the Julian calendar. The Romans had to periodically add a leap month every few years to keep the calendar year in
Unit of time year cannot be divided into 12 28-day months since 12 times 28 is 336, well short of 365. The lunar month (as defined by the moon's rotation) is not 28 days but 28.3 days. The year, defined in the Gregorian calendar as 365.24 days has to be adjusted with leap days and leap seconds. Consequently, these units are now all defined as multiples of seconds. Units of time based on orders of magnitude of the second include the nanosecond and the millisecond. The natural units for timekeeping used by most historical societies are the day, the solar year and the