Nabonassar

Nabonassar was a Babylonian king who ruled from 747 to 734 BCE. Later Greek astronomers used the beginning of his reign as an epoch for dating astronomical observations.

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Era of Nabonassar: An astronomical dating era beginning with Nabonassar’s accession in 747 BCE. This era turned the king’s accession into a fixed reference point for dated observations.
Babylonian king list: A chronological record of rulers and dynasties in ancient Babylonia. King lists provide the framework for locating Nabonassar’s reign among Babylonian rulers.
Berossus: A Babylonian priest and Greek-language historian who wrote about Babylonia in the early third century BCE. His history helped convey Babylonian royal chronology to Greek-speaking authors.
Babylonian calendar: A lunisolar calendar used in ancient Babylonia, with months tied to lunar cycles and seasons. Its dated months supplied the calendar context for observations associated with Nabonassar’s era.
Ptolemy: A second-century CE Greek astronomer and mathematician who wrote the Almagest. Ptolemy used the Era of Nabonassar when organizing historical astronomical observations.
Neo-Babylonian Empire: A Mesopotamian state that flourished under Chaldean rulers from the late seventh to sixth century BCE. Nabonassar ruled Babylonia before the later Neo-Babylonian Empire emerged.
Callippus: A fourth-century BCE Greek astronomer who refined the Metonic cycle into a 76-year period. His astronomical calendar belongs to the Greek tradition that later used Babylonian dated observations.
Regnal year: A year counted from a ruler’s accession or within a ruler’s reign. Nabonassar’s accession provided the starting point for counting years in the era named after him.
Almagest: Ptolemy’s Greek astronomical treatise, presenting a mathematical account of the heavens. Its dated records preserve the later astronomical use of Nabonassar’s epoch.
Nabû-nāṣir: The Akkadian form of the name Nabonassar, meaning “Nabu protects the king.” The name’s Babylonian form connects Greek accounts to the king’s native context.