Вавилонский лунно-солнечный календарь

Lunisolar calendar
The Babylonian calendar was a lunisolar calendar used in Mesopotamia from around the second millennium BCE until the Seleucid Era (294 BCE), and it was specifically used in Babylon from the Old Babylonian Period (1780 BCE) until the Seleucid Era. The civil lunisolar calendar was used contemporaneously with an administrative calendar of 360 days, with the latter used only in fiscal or astronomical contexts. The lunisolar calendar descends from an older Sumerian calendar used in the 4th and 3rd millennia BCE. The civil lunisolar calendar had years consisting of 12 lunar months, each beginning when a new crescent moon was first sighted low on the western horizon at sunset, plus an intercalary month inserted as needed, at first by decree and then later systematically according to what is now known as the Metonic cycle. Month names from the Babylonian calendar appear in the Hebrew calendar, Assyrian calendar, Syriac calendar, Old Persian calendar, and Turkish calendar.

As a lunisolar calendar, the civil calendar aimed to keep calendar months in sync with the synodic month and calendar years in sync with the tropical year. Since new months of the civil calendar were declared by observing the crescent moon, the calendar months could not drift from the synodic month. On the other hand, since the length of a calendar year was handled by the Metonic cycle starting after 499 BCE, there is some inherent drift present in the formulaic computation of the new year when compared to the true new year. While on any given year the first day of the first month could be up to 20 days off from the vernal equinox, on average the length of a year was very well approximated by the Metonic cycle; the computed average length is within 30 minutes of the true solar year length.

Since the civil calendar was not standardized and predictable for at least the first millennium of its use, a second calendar system thrived in Babylon during the same time spans, known today as the administrative or schematic calendar. The administrative year consisted of 12 months of exactly 30 days each. In the 4th and 3rd millennia BCE, extra months were occasionally intercalated (in which case the year is 390 days), but by the beginning of the 2nd millenium BCE it did not make any intercalations or modifications to the 360 day year. that Shabbat originally arose from the lunar cycle, containing four weeks ending in Sabbath, plus one or two additional unreckoned days per month. The difficulties of this theory include reconciling the differences between an unbroken week and a lunar week, and explaining the absence of texts naming the lunar week as Shabbat in any language. The rarely attested Sapattum or Sabattum as the full moon is cognate or merged with Hebrew Shabbat, but is monthly rather than weekly; it is regarded as a form of Sumerian sa bat ("mid rest"), attested in Akkadian as um nuh libbi ("day of mid repose"). 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." 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."

The Akkadian names for months surface in a number of calendars still used today. In Iraq and the Levant, the solar Gregorian calendar system is used, with Classical Arabic names replacing the Roman ones, and the month names in the Assyrian calendar descend directly from Aramaic, which descended from Akkadian. Similarly, while Turkey uses the Gregorian calendar in the present day, the names of Turkish months were inspired by the 1839 Rumi calendar of the Ottoman Empire, itself derived from the Ottoman fiscal calendar of 1677 based on the Julian calendar. This last calendar month names of both Syriac and Islamic origin, and in the modern calendar four of these names descend from the original Akkadian names.