
The Babylonian calendar was a
lunisolar calendar used in
Mesopotamia
Mesopotamia is a historical region of West Asia situated within the Tigris–Euphrates river system, in the northern part of the Fertile Crescent. Today, Mesopotamia is known as present-day Iraq and forms the eastern geographic boundary of ...
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
The Middle East (term originally coined in English language) is a geopolitical region encompassing the Arabian Peninsula, the Levant, Turkey, Egypt, Iran, and Iraq.
The term came into widespread usage by the United Kingdom and western Eur ...
and
Egypt
Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...
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
The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year (without exception). The Julian calendar is still used as a religious calendar in parts of the Eastern Orthodox Church and in parts ...
. As Anno Graecorum formed the basis for time references in the
Bible
The Bible is a collection of religious texts that are central to Christianity and Judaism, and esteemed in other Abrahamic religions such as Islam. The Bible is an anthology (a compilation of texts of a variety of forms) originally writt ...
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
The Hijri calendar (), also known in English as the Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the Ramad ...
as well as
Iranian calendars. The
Julian calendar
The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year (without exception). The Julian calendar is still used as a religious calendar in parts of the Eastern Orthodox Church and in parts ...
inherited the definitions of the 12
month
A month is a unit of time, used with calendars, that is approximately as long as a natural phase cycle of the Moon; the words ''month'' and ''Moon'' are cognates. The traditional concept of months arose with the cycle of Moon phases; such lunar mo ...
system,
week
A week is a unit of time equal to seven days. It is the standard time period used for short cycles of days in most parts of the world. The days are often used to indicate common work days and rest days, as well as days of worship. Weeks are ofte ...
,
hour etc. from the Babylonian calendar and the current
Jewish calendar
The Hebrew calendar (), also called the Jewish calendar, is a lunisolar calendar used today for Jewish religious observance and as an official calendar of Israel. It determines the dates of Jewish holidays and other rituals, such as ''yahrzeits ...
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
The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian cale ...
) therefore has its main structure inherited from the Babylonian calendar.
The Julian calendars have their month definitions in tabular form while the Babylonian calendar, the Jewish calendar, and the Muslim calendar have their months defined by the appearance of the new moon and
Iranian calendars by
solstice.
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 millennium BC
File:3rd millennium BC montage.jpg, 400x400px, From top left clockwise: Pyramid of Djoser; Khufu; Great Pyramid of Giza, one of the Seven Wonders of the Ancient World; Cuneiform, a contract for the sale of a field and a house; Enheduana, a high pr ...
.
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.
Civil calendar
The Babylonian civil calendar, also called the cultic calendar, was a lunisolar calendar descended from the Nippur calendar, which has evidence of use as early as 2600 BCE and descended from the even older
Third Dynasty of Ur (Ur III) calendar. The original Sumerian names of the months are seen in the orthography for the next couple millennia, albeit in more and more shortened forms. When the calendar came into use in Babylon circa 1780 BCE, the spoken month names became a mix from the calendars of the local subjugated cities, which were Akkadian. Historians agree that it was probably
Samsu-iluna who effected this change.
During the sixth century BCE
Babylonian captivity of the Jews, these month names were adopted into the
Hebrew calendar.
The first month of the civil calendar during the Ur III and Old Babylonian periods was ''Šekinku'' (Akk. ''Addaru''), or the month of barley harvesting, and it aligned with the
vernal equinox. However, during the intervening Nippur period, it was the twelfth month instead.
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.
Although this 19-year cycle is usually called the
Metonic cycle after
Meton of Athens (
432 BCE), the Babylonians used this cycle before Meton, and it may be that Meton learned of the cycle from the Babylonians. After no more than three isolated exceptions, by
380 BCE the months of the calendar were regulated by the cycle without exception. In the cycle of 19 years, the month ''Addaru'' ''2'' was intercalated, except in the year that was number 17 in the cycle, when the month ''Ulūlu 2'' was inserted instead.
During this period, the first day of each month (beginning at sunset) continued to be the day when a new crescent moon was first sighted—the calendar never used a specified number of days in any month. However, as astronomical science grew in Babylon, the appearance of the new moon was predictable with some accuracy into the short-term future. Still, during the
Neo-Assyrian period (c. 700 BCE) the calendar was sometimes retroactively "shifted back" a day to account for the fact that the king should have declared a new month, but only did so the following day because of
obstructive weather.
Accuracy
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.
Administrative calendar

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 millennium BCE it did not make any intercalations or modifications to the 360-day year.
This calendar saw use in areas requiring precision in dates or long-term planning; there is tablet evidence demonstrating it was used to date business transactions and
astronomical observations, and that
mathematics problems, wage calculations, and tax calculations all assumed the administrative calendar instead of the civil calendar.
Babylonian astronomers in particular made all astral calculations and predictions in terms of the administrative calendar. Discrepancies were accounted for in different ways according to the heavenly measurements being taken. When predicting the
phase of the moon, it was treated as if each ideal month began with a
new moon, even though this could not be true. In fact, this guideline appears in the MUL.APIN, which goes on further to specify that months that began "too early" (on the 30th of the previous month) were considered unlucky, and months that began "on time" (the day after the 30th of the previous month) were considered auspicious. When discussing the dates of
equinoxes and
solstices, the events were assigned fixed days of the administrative calendar, with
shortening or lengthening of intervening days taking place to ensure that the celestial phenomena would fall on the "correct" day. Which fixed day each phenomenon was assigned varied throughout time, for one because which month was designated first varied throughout history. In general, they were assigned to the 15th day of four equally spaced months.
Seven-day week and Sabbath
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 these days officials were prohibited from various activities and common men were forbidden to "make a wish", and at least the 28th was known as a "rest-day". 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
Shamash (Akkadian language, Akkadian: ''šamaš''), also known as Utu (Sumerian language, Sumerian: dutu "Sun") was the List of Mesopotamian deities, ancient Mesopotamian Solar deity, sun god. He was believed to see everything that happened in t ...
on the 21st, and
Enki and
Mah on the 28th. Tablets from the sixth-century BC reigns of
Cyrus the Great
Cyrus II of Persia ( ; 530 BC), commonly known as Cyrus the Great, was the founder of the Achaemenid Empire. Achaemenid dynasty (i. The clan and dynasty) Hailing from Persis, he brought the Achaemenid dynasty to power by defeating the Media ...
and
Cambyses II indicate these dates were sometimes approximate. The
lunation of 29 or 30 days basically contained three
seven-day weeks, and a final week of eight or nine days inclusive, breaking the continuous seven-day cycle.
Among other theories of ''
Shabbat'' origin, the ''Universal Jewish Encyclopedia'' of
Isaac Landman advanced a theory of
Assyriologists like
Friedrich Delitzsch 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 ''Sapattu
m'' or ''Sabattu
m'' 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: "
abath shalt thou then encounter, mid
onthy."
Impact
The Akkadian names for months surface in a number of calendars still used today. In
Iraq
Iraq, officially the Republic of Iraq, is a country in West Asia. It is bordered by Saudi Arabia to Iraq–Saudi Arabia border, the south, Turkey to Iraq–Turkey border, the north, Iran to Iran–Iraq border, the east, the Persian Gulf and ...
and the
Levant, the solar
Gregorian calendar
The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian cale ...
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
The Ottoman Empire (), also called the Turkish Empire, was an empire, imperial realm that controlled much of Southeast Europe, West Asia, and North Africa from the 14th to early 20th centuries; it also controlled parts of southeastern Centr ...
, itself derived from the Ottoman fiscal calendar of 1677 based on the
Julian calendar
The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year (without exception). The Julian calendar is still used as a religious calendar in parts of the Eastern Orthodox Church and in parts ...
. 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.
See also
Lunisolar calendars
*
Hebrew calendar
*
Ancient Macedonian calendar
Other systems
*
Assyrian calendar
*
Mandaean calendar
*
Persian calendar
*
Islamic calendar
The Hijri calendar (), also known in English as the Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the Ramad ...
*
Solar Hijri calendar
The Solar Hijri calendar is the official calendar of Iran. It is a solar calendar, based on the Earth's orbit around the Sun. Each year begins on the day of the March equinox and has years of 365 or 366 days. It is sometimes also called the S ...
*
Pre-Islamic Arabian calendar
*
Babylonian astrology
*
Babylonian astronomy
Babylonian astronomy was the study or recording of celestial objects during the early history of Mesopotamia. The numeral system used, sexagesimal, was based on 60, as opposed to ten in the modern decimal system. This system simplified the ca ...
*
Arabic names of Gregorian months
*
MUL.APIN
*
Egyptian,
Coptic, and
Ethiopian calendars
*
Zoroastrian and
Armenian calendars
*
Turkish months
References
Citations
Bibliography
*Parker, Richard Anthony and Waldo H. Dubberstein. ''Babylonian Chronology 626 BC.–AD. 75''. Providence, RI: Brown University Press, 1956.
*W. Muss-Arnolt, ''The Names of the Assyro-Babylonian Months and Their Regents'', Journal of Biblical Literature (1892).
*Sacha Stern, "The Babylonian Calendar at Elephantine" in ''Zeitschrift für Papyrologie und Epigraphik'' 130 (2000) 159–171
PDF document 94 KB)
*Fales, Frederick Mario, “A List of Umma Month Names”, Revue d’assyriologie et d’archéologie orientale, 76 (1982), 70–71.
* Gomi, Tohru, “On the Position of the Month iti-ezem-dAmar-dSin in the Neo-Sumerian Umma Calendar”, Zeitschrift für Assyriologie und Vorderasiatische Archäologie, 75 (1985), 4–6.
* Pomponio, Francesco, “The Reichskalender of Ur III in the Umma Texts”, Zeitschrift für Assyriologie und Vorderasiastische Archäologie, 79 (1989), 10–13.
* Verderame, Lorenzo, “Le calendrier et le compte du temps dans la pensée mythique suméro-akkadienne”, De Kêmi à Birit Nâri, Revue Internationale de l'Orient Ancien, 3 (2008), 121–134.
* Steele, John M., ed., "Calendars and Years: Astronomy and Time in the Ancient Near East", Oxford: Oxbow, 2007.
External links
{{Portal bar, Asia, Astronomy
Obsolete calendars
Calendar
A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A calendar date, date is the designation of a single and specific day within such a system. A calendar is ...
Lunisolar calendars