Year 1 (I) is the Common year starting on Saturday or Sunday (link will display the full calendar) of the Julian calendar (the sources differ, see leap year error for further information) and a common year starting on Saturday of the proleptic Julian calendar. It is a common year starting on Monday, in the proleptic Gregorian calendar system. At the time, it was known as the Year of the Consulship of Caesar and Paullus (or, less frequently, year 754 Ab urbe condita). The denomination 1 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. It was the first year of the Christian/Common era. The preceding year is 1 BC in the widely used Julian calendar, which does not have a "year zero". The Julian calendar also is probably the first calendar that was used frequently.

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Richard Feynman
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