Anno Mundi in the context of "Genesis flood narrative"

The Babylonian calendar was a lunisolar calendar used in Mesopotamia from around the 2nd millennium BC until the Seleucid Era (294 BC), and it was specifically used in Babylon from the Old Babylonian Period (1780s BC) until the Seleucid Era.

In the Seleucid Era it was reformed as "Greek time", Anno Graecorum was introduced and used in the Middle East and Egypt until the middle of the first millennium when the First Council of Nicaea AD 325 defined the Church year based on the Roman early Julian calendar. As Anno Graecorum formed the basis for time references in the Bible and spread westward, it rather increased the Babylonian calendars importance. The Babylonian calendar is also partly reflected in calendars in South and East Asia and the Islamic calendar as well as Iranian calendars. The Julian calendar inherited the definitions of the 12 month system, week, hour etc. from the Babylonian calendar and the current Jewish calendar can be seen as a slightly modified Babylonian calendar that still exists today and is practised, but with Anno Mundi Livryat haOlam year calculation since the creation of the world. Today's global time system UTC (Gregorian calendar) therefore has its main structure inherited from the Babylonian calendar.

The chronology of the Bible is an elaborate system of lifespans, "generations", and other means by which the Masoretic Hebrew Bible (the text of the Bible most commonly in use today) measures the passage of events from the creation to around 164 BCE (the year of the re-dedication of the Second Temple). It was theological in intent, not historical in the modern sense, and functions as an implied prophecy whose key lies in the identification of the final event. The passage of time is measured initially by adding the ages of the Patriarchs at the birth of their firstborn sons, later through express statements, and later still by the synchronised reigns of the kings of Israel and Judah.

The chronology is highly schematic, marking out a world cycle of 4,000 years. The Exodus takes place in the year A.M. 2666 (Anno Mundi, years since the creation of the world), exactly two-thirds of the way through the 4,000-year period: the construction of Solomon's Temple commences 480 years afterward—12 generations of 40 years each—and 430 years pass between the building of Solomon's Temple and its destruction during the siege of Jerusalem. The 50 years between the destruction of the Temple and the "Decree of Cyrus" and end of the Babylonian Exile, added to the 430 years for which the Temple stood, produces another symmetrical period of 480 years. The 374 years between the Edict of Cyrus and the re-dedication of the Second Temple by the Maccabees complete the 4,000-year cycle.

A calendar date is a reference to a particular day, represented within a calendar system, enabling a specific day to be unambiguously identified. Simple math can be performed between dates; commonly, the number of days between two dates may be calculated, e.g., "25 December 2025" is ten days after "15 December 2025". The date of a particular event depends on the time zone used to record it. For example, the air attack on Pearl Harbor that began at 7:48 a.m. local Hawaiian time (HST) on 7 December 1941 is recorded equally as having happened on 8 December at 3:18 a.m. Japan Standard Time (JST).

A particular day may be assigned a different nominal date according to the calendar used. The de facto standard for recording dates worldwide is the Gregorian calendar, the world's most widely used civil calendar. Many cultures use religious calendars such as the Gregorian (Western Christendom, AD), the Julian calendar (Eastern Christendom, AD), Hebrew calendar (Judaism, AM), the Hijri calendars (Islam, AH), or any other of the many calendars used around the world. Regnal calendars (that record a date in terms of years since the beginning of the monarch's reign) are also used in some places, for particular purposes.

The civil calendar is the calendar, or possibly one of several calendars, used within a country for civil, official, or administrative purposes. The civil calendar is almost always used for general purposes by people and private organizations.

The most widespread civil calendar and de facto international standard is the Gregorian calendar. Although that calendar was first declared by Pope Gregory XIII to be used in Catholic countries in 1582, it has since been adopted, as a matter of convenience, by many secular and non-Christian countries, although some countries use other calendars.

The Hijri era (Arabic: التقويم الهجري, romanized: at-taqwīm al-hijrī) is the calendar era used to record dates in the Islamic world. Its epoch (start point of the era) is the year in which Muhammad and his followers migrated from Mecca to Yathrib (now Medina), in 622 CE. This event, known as the Hijrah, is commemorated in Islam for its role in the founding of the first Muslim community (ummah). Time in this era is measured by two principal calendars: the lunar Hijri calendar (known in the West as the "Islamic calendar") which counts lunar years since the Hijrah and which is used by most Muslims around the world; and the solar Hijri calendar (also known as the "Persian calendar") which counts solar years since the Hijrah and which is used in Iran.

In the West, dates in the lunar Hijri calendar are denoted as AH (Latin: Anno Hegirae) or Hijri year (Arabic: سنة هجرية, romanized: sanat hijriyya, lit. 'in the year of the Hijra') in the style of the Christian/Common (AD/CE) and Jewish eras (AM) and can similarly be placed before (preferably) or after the date. In predominantly Muslim countries, it is also commonly abbreviated H ("Hijra") from its Arabic abbreviation hāʾ (هـ). Years prior to AH 1 are reckoned in English as BH ("Before the Hijra"), which follows the date. Dates in the solar Hijri calendar are denoted as SH. The current year according to the lunar Hijri calendar is AH 1447; according to the solar Hijri calendar the current year is SH 1404. The difference in numbering arises because a lunar year is about eleven days shorter than a solar year.

The Mishneh Torah (Hebrew: מִשְׁנֵה תוֹרָה, lit. 'repetition of the Torah'), also known as Sefer Yad ha-Hazaka (ספר יד החזקה, 'book of the strong hand'), is a code of Rabbinic Jewish religious law (halakha) authored by Maimonides (Rabbi Moshe ben Maimon/Rambam). The Mishneh Torah was compiled between 1170 and 1180 CE (4930 and 4940 AM), while Maimonides was living in Egypt, and is regarded as Maimonides' magnum opus. Accordingly, later sources simply refer to the work as "Maimon", "Maimonides", or "RaMBaM", although Maimonides composed other works.

Mishneh Torah consists of fourteen books, subdivided into sections, chapters, and paragraphs. It is the only medieval-era work that details all of Jewish observance, including those laws that are only applicable when the Temple in Jerusalem is in existence, and remains an important work in Judaism.

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; lit. 'Roman year since the creation of the universe', abbreviated as ε.Κ.), 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 it was used in 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 as the "Serbian Calendar" and today still used in the Republic of Georgia alongside Old Style and New Style calendar.

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 2025) 7534 (7533 before September 1).