What does 331 mean in US Phone Area Codes?

331

Year 331 (CCCXXXI) was a common year starting on Friday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Bassus and Ablabius (or, less frequently, year 1084 Ab urbe condita). The denomination 331 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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