Anno Mundi

Anno Mundi (from Latin "in the year of the world"; Hebrew: לבריאת העולם, romanized: Livryat haOlam, lit. 'to the creation of the world'), abbreviated as AM or A.M., or Year After Creation,^[1] is a calendar era based on the biblical accounts of the creation of the world and subsequent history. Two such calendar eras have seen notable use historically:

• Since the Middle Ages, the Hebrew calendar has been based on rabbinic calculations of the year of creation from the Hebrew Masoretic Text of the Bible. This calendar is used within Jewish communities for religious purposes and is one of two official calendars in Israel. In the Hebrew calendar, the day begins at sunset. The calendar's epoch, corresponding to the calculated date of the world's creation, is equivalent to sunset on the Julian proleptic calendar date 6 October 3761 BCE.^[2] The new year begins at Rosh Hashanah, in Tishrei. Anno mundi 5784 (meaning the 5,784th year since the creation of the world) began at sunset on 15 September 2023 according to the Gregorian calendar.^[3]
• The Byzantine calendar was used in the Eastern Roman Empire and many Christian Orthodox countries and Eastern Orthodox Churches and was based on the Septuagint text of the Bible. That calendar is similar to the Julian calendar except that its reference date is equivalent to 1 September 5509 BCE on the Julian proleptic calendar.

While both calendars reputedly counted the number of years since the creation of the world, the primary reason for their disparity lies in which underlying biblical text is chosen (the Earth seems to have been created roughly around 5500 BCE based on the Greek Septuagint text, and about 3760 BCE based on the Hebrew Masoretic text). Most of the 1,732-year difference resides in numerical discrepancies in the genealogies of the two versions of the Book of Genesis. Patriarchs from Adam to Terah, the father of Abraham, are said to be older by 100 years or more when they begat their named son in the Greek Septuagint^[4][5] than they were in the Latin Vulgate,^[6] or the Hebrew Tanakh.^[7] The net difference between the two major genealogies of Genesis is 1,466 years (ignoring the "second year after the flood" ambiguity), 85% of the total difference. (See Dating creation.)^{[original research?]}

There are also discrepancies between methods of dating based on the text of the Bible vs. modern academic dating of landmark events used to calibrate year counts, such as the destruction of the First Temple—see Missing years (Jewish calendar).