#] #] ********************* #] "$d_projMin"'calendars/History of calendars, notes.txt' # www.BillHowell.ca 13Jan2026 initial # view in text editor, using constant-width font (eg courier), tabWidth = 3 # Read-Eval-Print Loop (REPL) is typically running in a terminal in workspace 3 # backup this file: REPL$ sudo pinn_arcArch "$d_bin"'0_form notes.txt' # backup workspace example: REPL$ sudo pinnL_arcArch "$d_bin"'start/base_WkSpc.sh REPL pLst.txt' # note that 'base_WkSpc.sh REPL pLst.txt' can be used far beyond just backups!! #48************************************************48 #24************************24 # Table of Contents, generate with : # $ grep "^#]" "$d_projMin"'calendars/History of calendars, notes.txt' | sed "s|^#\]| |" >"$d_projMin"'calendars/History of calendars, notes.txt'' TblOfCont.txt' # # +--+ build summary of key points : #kp# #kp# ********************* #kp# "$d_projMin"'calendars/History of calendars, notes.txt' #kp# # $ grep "^#kp#" "$d_projMin"'calendars/History of calendars, notes.txt' | sed 's|^#kp#| |' >"$d_projMin"'calendars/History of calendars, notes.txt'' key points.txt' #24************************24 # Setup, ToDos, #08********08 #] ??Jan2026 #08********08 #] ??Jan2026 #08********08 #] ??Jan2026 #08********08 #] ??Jan2026 #08********08 #] ??Jan2026 #08********08 #] ??Jan2026 +-----+ https://en.wikipedia.org/wiki/History_of_calendars The first historically attested and formulized calendars date to the Bronze Age, dependent on the development of writing in the ancient Near East. The Yoruba people of West Africa have one of the oldest recorded calendars in human history. It is one of the oldest verified calendar systems in the world used by a continuing culture. Known as Kojoda, the Yoruba calendar dates back over 10,067 years as of 2025, meaning its origin can be traced to approximately 8042 BC. [1] In Victoria, Australia, a Wurdi Youang stone arrangement undergoing research could date back more than 11,000 years.[2] In 2013, archaeologists unearthed ancient evidence of a 10,000-year-old calendar system in Warren Field, Aberdeenshire.[3] This calendar is the next earliest, or "the first Scottish calendar". The Sumerian calendar was the next earliest, followed by the Egyptian, Assyrian and Elamite calendars. Calendars in antiquity were usually lunisolar, depending on the introduction of intercalary months to align the solar and the lunar years. This was mostly based on observation, but there may have been early attempts to model the pattern of intercalation algorithmically, as evidenced in the fragmentary 2nd-century Coligny calendar. The Roman calendar was reformed by Julius Caesar in 45 BC. The Julian calendar was no longer dependent on the observation of the new moon but simply followed an algorithm of introducing a leap day every four years. This created a dissociation of the calendar month from the lunation. In the 11th century in Persia, a calendar reform led by Khayyam was announced in 1079, when the length of the year was measured as 365.24219858156 days.[5] Given that the length of the year is changing in the sixth decimal place over a person's lifetime, this is outstandingly accurate. For comparison the length of the year at the end of the 19th century was 365.242196 days, while at the end of the 20th century it was 365.242190 days.[5][6] +--+ Prehistory Many Upper Paleolithic cave paintings of animals from across western and central Europe are accompanied by sequences of dots and lines. It has been hypothesized that these are tally marks representing lunar months, with the year beginning at the end of winter. A branching "Y" symbol represents mating or birthing month for the associated animal, making each sequence a phenological calendar.[7] A number of prehistoric structures have been proposed as having had the purpose of timekeeping (typically keeping track of the course of the solar year). This includes many megalithic structures, and reconstructed arrangements going back far into the Neolithic period. In Victoria, Australia, a Wurdi Youang stone arrangement could date back more than 11,000 years.[2] This estimate is based on the inaccuracy of the calendar, which is consistent with how the Earth's supposed orbit is thought to have changed during that time.[clarification needed][8] The site is found near the world's oldest known site of permanent aquaculture. A Mesolithic arrangement of twelve pits and an arc found in Warren Field, Aberdeenshire, Scotland, dated to roughly 8,000 BC, has been described as a lunar calendar and was dubbed the "world's oldest known calendar" in 2013.[9] +--+ Ancient Sumerian The ancient Sumerian calendar, roughly dated to 2100 BC, divided a year into 12 lunar months of 29 or 30 days.[10] Each month began with the sighting of a new moon. Sumerian months had no uniform name throughout Sumer because of the religious diversity.[11] This resulted in scribes and scholars referring to them as "the first month", "the fifth month", etc.[citation needed] To keep the lunar year of 354 days in step with the solar year of 365.242 days an extra month was added periodically, much like a Gregorian leap year.[11] There were no weeks in the Sumerian calendar.[12] Holy days and time off from work were usually celebrated on the first, seventh and fifteenth of each month. In addition to these holy days, there were also feast days which varied from city to city.

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13Jan2026 https://en.wikipedia.org/wiki/Babylonian_calendar

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 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.[1] The lunisolar calendar descends from an older Sumerian calendar used in the 4th and 3rd millennium BC.[2]

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.[3]

Month names from the Babylonian calendar appear in the Hebrew calendar, Assyrian calendar, Syriac calendar, Old Persian calendar, and Turkish calendar.

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13Jan2026 Duck.ai: Overview of the Babylonian Calendar System [Wikipedia, Encyclopedia Britannica]

The Babylonian calendar was a lunisolar calendar used in ancient Mesopotamia from around the 2nd millennium BC until the Seleucid Era (294 BC). It was primarily utilized in Babylon from the Old Babylonian Period (circa 1780 BC) onward.

Structure of the Calendar Key Features
Feature Description
Civil Calendar A lunisolar calendar with months based on lunar phases.
Administrative Calendar A separate calendar with 12 months of 30 days each, used for precise record-keeping.
Month Names Many month names from the Babylonian calendar influenced the Hebrew calendar.
Cultural Impact The calendar's structure influenced various other calendars, including the Jewish and Islamic calendars.

Historical Significance

The Babylonian calendar played a crucial role in regulating civil life, religious observances, and agricultural activities. Its month names and structure were adopted by the Jewish people during the Babylonian captivity, which significantly impacted the development of the Jewish calendar. The calendar's influence extended to other cultures in the Near East and beyond, shaping timekeeping practices for centuries.


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