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, 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.

Versions

Two different variations of the Seleucid years existed, one where the year started in spring and another where it starts in autumn: These differences in the beginning of the year means that dates differ by one if they fall between spring and autumn. Notably, the Jewish historical book 1 Maccabees generally uses the Babylonian and Judean year count (,, 9:3, 10:1, etc.). However, the book 2 Maccabees exclusively uses the Macedonian version of the calendar, likely because it was written in either Cyprus or Egypt. Elias Bickerman gives this example:

Later usage

The Seleucid era was used as late as the sixth century CE, for instance in the Zabad inscription in Syria, dated the 24th of Gorpiaios, 823 (24 September, 512 AD), and in the writings of John of Ephesus. Syriac chroniclers continued to use it up to Michael the Syrian in the 12th century AD / 15th century AG. It has been found on Central Asian tombstones of Christians belonging to the Church of the East well into the 14th century AD. The Seleucid era counting, or "era of contracts" (minyan shəṭarot), was used by Yemenite Jews in their legal deeds and contracts until modern times, a practice derived from an ancient Jewish teaching in the Talmud, requiring all Diaspora Jews to uphold its practice. For this reason, the Seleucid era counting is mentioned in the Book of Maccabees (I Macc. i. 11) and in the writings of the historian Josephus. The Seleucid era counting fell into disuse among most Jewish communities, following Rabbi David ben Zimra's cancellation of the practice when he served as Chief Rabbi of Egypt.