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The Byzantine calendar, also called the Roman calendar, the Creation Era of Constantinople or the Era of the World (Ancient Greek: Ἔτη Γενέσεως Κόσμου κατὰ Ῥωμαίους, also Ἔτος Κτίσεως Κόσμου or Ἔτος Κόσμου, abbreviated as ε.Κ.; literal translation of Ancient Greek Roman year since the creation of the universe), was the calendar used by the Eastern Orthodox Church from c. 691 to 1728 in the Ecumenical Patriarchate. It was also the official calendar of the Byzantine Empire from 988 to 1453 and of Kievan Rus' and Russia from c. 988 to 1700. This calendar was used also in other areas of the Byzantine commonwealth such as in Serbia, where it is found in old Serbian legal documents such as Dušan's Code, thus being referred to as the Serbian Calendar as well. Since Byzantine is a historiographical term, the original name uses the adjective "Roman" as it was what the Eastern Roman Empire continued calling itself.
The calendar was based on the Julian calendar, except that the year started on 1 September and the year number used an Anno Mundi epoch derived from the Septuagint version of the Bible. It placed the date of creation at 5509 years before the incarnation of Jesus, and was characterized by a certain tendency that had already been a tradition among Jews and early Christians to number the years from the calculated foundation of the world (Latin: Annus Mundi or Ab Origine Mundi— "AM"). Its Year One, marking the assumed date of creation, was September 1, 5509 BC, to August 31, 5508 BC. This would make the current year (AD 2023) 7532 (7531 before September 1; and 7532 after September 1).