Seleucid era

The Seleucid era ("SE") or Anno Graecorum (literally "year of the Greeks" or "Greek year"), sometimes denoted "AG," was a system of numbering years in use by the Seleucid Empire and other countries among the ancient Hellenistic civilizations, and later by the Parthians. It is sometimes referred to as "the dominion of the Seleucidæ," or the Year of Alexander. The era dates from Seleucus I Nicator's reconquest of Babylon in 312/11 BC after his exile in Ptolemaic Egypt,¹ considered by Seleucus and his court to mark the founding of the Seleucid Empire. According to Jewish tradition, it was during the sixth year of Alexander the Great's reign (lege: possibly Alexander the Great's infant son, Alexander IV of Macedon) that they began to make use of this counting.²

Versions

Two different variations of the Seleucid years existed, one where the year started in spring and another where it starts in autumn:

1. The natives of the empire used the Babylonian calendar, in which the new year falls on 1 Nisanu (3 April in 311 BC), so in this system year 1 of the Seleucid era corresponds roughly to April 311 BC to March 310 BC. This included the inhabitants of Coele-Syria, notably the Jews who call it the Era of Contracts (Hebrew: מניין שטרות, romanized: minyān shəṭarōṯ).
2. The Macedonian court adopted the Babylonian calendar (substituting the Macedonian month names) but reckoned the new year to be in the autumn (the exact date is unknown). In this system year 1 of the Seleucid era corresponds to the period from autumn 312 BC to summer 311 BC. By the 7th century AD / 10th AG, the west Syrian Christians settled on 1 October-to-30 September. Jews, however, reckon the start of each new Seleucid year with the lunar month .