History of calendars
The history of calendars covers practices with ancient roots as people created and used various methods to keep track of days and larger divisions of time.
The first historically attested and formulized calendars date to the Bronze Age, dependent on the development of writing in the ancient Near East.
One of several regional Hindu calendars in use on the Indian subcontinent, it is based on twelve synodic lunar months and 365 solar days.
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 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.
Many Upper Paleolithic cave paintings of animals from across western and central Europe are accompanied by sequences of dots and lines.
[12] Old Persian inscriptions and tablets indicate that early Iranians used a 360-day calendar based on the solar observation directly and modified for their beliefs.
The unified Achaemenid Empire required a distinctive Iranian calendar, and one was devised in Egyptian tradition, with 12 months of 30 days, each dedicated to a yazata (Eyzad), and four divisions resembling the Semitic week.
Thirteen days were named after Fire, Water, Sun, Moon, Tiri and Geush Urvan (the soul of all animals), Mithra, Sraosha (Soroush, yazata of prayer), Rashnu (the Judge), Fravashi, Bahram (yazata of victory), Raman (Ramesh meaning peace), and Vata, the divinity of the wind.
The remaining four were dedicated to Asman (lord of sky or Heaven), Zam (earth), Manthra Spenta (the Bounteous Sacred Word) and Anaghra Raocha (the 'Endless Light' of paradise).
For example, in Achaemenid times the modern Persian month 'Day' was called Dadvah (Creator), in Parthian it was Datush, and the Sassanians named it Dadv/Dai (Dadar in Pahlavi).
Toghril Beg, the founder of the Seljuq dynasty, had made Esfahan the capital of his domains and his grandson Malik-Shah was the ruler of that city from 1073.
Other leading astronomers were also brought to the Observatory in Esfahan and for 18 years Khayyam led the scientists and produced work of outstanding quality.
Cowell quotes the Calcutta Review No 59: When the Malik Shah determined to reform the calendar, Omar was one of the eight learned men employed to do it, the result was the Jalali era (so called from Jalal-ud-din, one of the king's names) – 'a computation of time,' says Gibbon, 'which surpasses the Julian, and approaches the accuracy of the Gregorian style.
See About the structure of the Attic Calendar The Athenian months were called Hekatombion, Metageitnion, Boedromion, Pyanepsion, Maimakterion, Poseidon, Gamelion, Anthesterion, Elaphebolion, Munychion, Thargelion, and Skirophorion.
The table of Greek Olympiads, following the four-year cycles between the Olympic Games from 1 July 776 BC, continued until the end of the 4th century AD.
[16] Romans from the same family often had the same praenomen, which sometimes makes it difficult to distinguish them, and there were two consuls at any one time, each of whom might sometimes hold the appointment more than once, meaning that it was (and is) necessary to be well educated in history to understand the references.
[21][22][23] This study was one of the six ancient Vedangas, or ancillary science connected with the Vedas – the scriptures of Hinduism, which was quoted by 5th-century BC scholar Yaska.
[25] The Jyotisha text Brahma-siddhanta, probably composed in the 5th century AD, discusses how to use the movement of planets, sun and moon to keep time and calendar.
[28][29] The Jyotisha texts present mathematical formulae to predict the length of day time, sun rise and moon cycles.
However the ancient historian Livy gave credit to the second early Roman king Numa Pompilius for devising a calendar of 12 months.
A Carolingian-era calendar published by Luc d'Achery is entitled Incipit Ordo Solaris Anni cum Litteris a S. Hieronymo superpositis, ad explorandum Septimanae Diem, et Lunae Aetatem investigandam in unoquoque Die per xix Annos.
[41] The Leiden Aratea, a Carolingian copy (dated 816) of an astronomical treatise of Germanicus, is an important source for the transmission of the ancient Christian calendar to the medieval period.
[43] According to the Catholic Encyclopedia, even Popes continued to date documents according to regnal years, and usage of AD only gradually became common in Europe from the 11th to the 14th centuries.
In 1267, the medieval scientist Roger Bacon stated the times of full moons as a number of hours, minutes, seconds, thirds, and fourths (horae, minuta, secunda, tertia, and quarta) after noon on specified calendar dates.
[16] For chronological purposes, the flaw of the Anno Domini system was that dates have to be reckoned backwards or forwards according as they are BC or AD.
The Xhosa year traditionally begins in June and ends in May when one of the brightest stars visible in the Southern Hemisphere, Canopus, signals the time for harvesting.
[56] The Sacred Round of 260 days is composed of two smaller cycles: the numbers 1 through 13, coupled with 20 different day names: Imix, Ik, Akbal, Kan, Chicchan, Cimi, Manik, Lamat, Muluc, Oc, Chuen, Eb, Ben, Ix, Men, Cib, Caban, Eiznab, Cauac, and Ahau.
The Sacred Round was used to determine important activities related to the gods and humans: name individuals, predict the future, decide on auspicious dates for battles, marriages, and so on.
The 18 Maya months are known, in order, as: Pop, Uo, Zip, Zotz, Tzec, Xuc, Yaxkin, Mol, Chen, Yax, Zac, Ceh, Mac, Kankin, Maun, Pax, Kayab and Cumku.
