Today we mark the 1540 birth of Joseph Justus Scaliger, the French scholar honored as the founder of scientific chronology. In 1583, at the age of 43, during the middle of the Gregorian calendar reform, Scaliger proposed what is known as the Julian period, a chronological period generally considered to have been named after his late father (Julius Caesar Scaliger) or perhaps after Gaius Julius Caesar, who had been dead for more than 1,500 years and after whom the Julian calendar is named. (来源：http://www.EnglishCN.com)

The Julian period is a chronological period of 7,980 Julian years. It combines the solar and lunar cycles together with the Roman indiction cycle, and it is considered to have brought order to ancient chronology.

The Julian period is reckoned from—that is, it is considered to have begun in—the year 4,713 B.C., when the first years of these cycles coincided. Solar and lunar cycles are easy enough to figure out, but what is the Roman indiction calendar? Indiction, from the Latin word for "proclamation," names a 15-year cycle used as a chronological unit in several ancient and medieval systems. In addition to Roman indiction, the cycle is also known as pontifical indiction and simply indiction.

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