What does 401 mean in HTTP Error Codes?

401

Year 401 (CDI) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Vincentius and Fravitus (or, less frequently, year 1154 Ab urbe condita). The denomination 401 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.

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