Babylonian calendar

In the Seleucid Era it was reformed as "Greek time", Anno Graecorum was introduced and used in the Hellenistic and Jewish worlds of the Middle East and Egypt until the middle of the first millennium when Islam conquered Babylon and 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.

[3] During the sixth century BCE Babylonian captivity of the Jews, these month names were adopted into the Hebrew calendar.

[3] Until the 5th century BCE, the calendar was fully observational, and the intercalary month was inserted approximately every two to three years, at first by guidelines which survive in the MUL.APIN tablet.

Beginning in around 499 BCE, the intercalation began to be regulated by a predictable lunisolar cycle, so that 19 years comprised 235 months.

[3] Counting from the new moon, the Babylonians celebrated every seventh day as a "holy-day", also called an "evil-day" (meaning "unsuitable" for prohibited activities).

On each of them, offerings were made to a different god and goddess, apparently at nightfall to avoid the prohibitions: Marduk and Ishtar on the 7th, Ninlil and Nergal on the 14th, Sin and Shamash on the 21st, and Enki and Mah on the 28th.

Tablets from the sixth-century BC reigns of Cyrus the Great and Cambyses II indicate these dates were sometimes approximate.

[13] Among other theories of Shabbat origin, the Universal Jewish Encyclopedia of Isaac Landman advanced a theory of Assyriologists like Friedrich Delitzsch[14] that Shabbat originally arose from the lunar cycle,[15][16] containing four weeks ending in Sabbath, plus one or two additional unreckoned days per month.

According to Marcello Craveri, Sabbath "was almost certainly derived from the Babylonian Shabattu, the festival of the full moon, but, all trace of any such origin having been lost, the Hebrews ascribed it to Biblical legend.

"[19] This conclusion is a contextual restoration of the damaged Enûma Eliš creation account, which is read as: "[Sa]bbath shalt thou then encounter, mid[month]ly.