AD 1

AD 1 (I) or 1 CE was a common year starting on Saturday or Sunday,^{[note 1]} a common year starting on Saturday by the proleptic Julian calendar, and a common year starting on Monday by the proleptic Gregorian calendar. It is the epoch year for the Anno Domini (AD) Christian calendar era, and the 1st year of the 1st century and 1st millennium of the Christian or Common Era (CE).

In the Roman Empire, AD 1 was known as the "Year of the consulship of Gaius Caesar and Lucius Paullus",^[1] and less frequently, as the year AUC 754 (see ab urbe condita). The denomination "AD 1" for this year has been in consistent use since the mid-medieval period when the Anno Domini (AD) calendar era became the prevalent method in Europe for naming years. It was the beginning of the Christian era/common era. The preceding year is 1 BC; there is no year 0 in this numbering scheme. The Anno Domini dating system was devised in AD 525 by Dionysius Exiguus.

The Julian calendar, a 45 BC reform of the Roman calendar, was the calendar used by Rome in AD 1.

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