Egyptian calendar#Ptolemaic and Roman

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| quote = Setting a calendar by the Nile flood would be about as vague a business as if we set our calendar by the return of the Spring violets.

| source = —H.E. Winlock{{harvp|Winlock|1940|p=[https://archive.org/stream/H.e.WinlockTheOriginOfTheAncientEgyptianCalendar1840/Winlock_originOfTheAncientEgyptianCalendar_procAmerPhilosophSoc_1940_sep_v83_n3_447-464#page/n3/mode/2up 450]}}.

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File:WEBSTER(1830) 2.011 OVERFLOW OF THE NILE. VIEWFROM THE PYRAMIDS, LOOKING TOWARDS CAIRO.jpg {{c.|1830}}.]]

Current understanding of the earliest development of the Egyptian calendar remains speculative. A tablet from the reign of the First Dynasty pharaoh Djer ({{c.|3000}}{{nbsp}}BC) was once thought to indicate that the Egyptians had already established a link between the heliacal rising of Sirius ({{langx|egy|Spdt}} or Sopdet, "Triangle"; {{langx|grc|{{linktext|Σῶθις}}}}, Sôthis) and the beginning of their year, but more recent analysis has questioned whether the tablet's picture refers to Sirius at all.{{sfnp|Clagett|1995|pp=10–11}} Similarly, based on the Palermo Stone, Alexander Scharff proposed that the Old Kingdom observed a 320-day year, but his theory has not been widely accepted.{{sfnp|Winlock|1940}} Some evidence suggests the early civil calendar had 360 days,{{harvp|Tetley|2014|p=[https://www.egyptchronology.com/wp-content/uploads/2021/08/The-Reconstructed-Chronology-of-the-Egyptian-Kings-2017-Internet.pdf 40]}}. although it might merely reflect the unusual status of the five epagomenal days as days "added on" to the proper year.

With its interior effectively rainless for thousands of years,{{sfnp|Winlock|1940|p=452}} ancient Egypt was "a gift of the river" Nile,{{citation |author=Herodotus |author-link=Herodotus |title=Histories |at=[http://www.sacred-texts.com/cla/hh/hh2000.htm Book II, §5] |editor-last=Macaulay |editor-link=George Campbell Macaulay |date=1890 |location=London |publisher=Macmillan }}. whose annual flooding organized the natural year into three broad natural seasons known to the Egyptians as:{{harvp|Tetley|2014|p=[https://www.egyptchronology.com/wp-content/uploads/2021/08/The-Reconstructed-Chronology-of-the-Egyptian-Kings-2017-Internet.pdf 39]}}.{{sfnp|Winlock|1940|p=453}}{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA4 4–5]}}

1. Inundation or Flood ({{langx|egy|Ꜣḫt}}, sometimes anglicized as Akhet): roughly from September to January.
2. Emergence or Winter ({{lang|egy|Prt}}, sometimes anglicized as Peret): roughly from January to May.
3. Low Water or Harvest or Summer ({{lang|egy|Šmw}}, sometimes anglicized as Shemu): roughly from May to September.

As early as the reign of Djer ({{c.|3000}}{{nbsp}}BC, Dynasty I), yearly records were being kept of the flood's high-water mark.{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA33 33]}} Otto E. Neugebauer noted that a 365-day year can be established by averaging a few decades of accurate observations of the Nile flood without any need for astronomical observations,{{sfnp|Neugebauer|1939}} although the great irregularity of the flood from year to year{{efn|In the 30 years prior to the completion of the Aswan Low Dam in 1902, the period between Egypt's "annual" floods varied from 335 to 415 days, with the first rise starting as early as 15 April and as late as 23 June.{{sfnp|Parker|1950|p=32}}}} and the difficulty of maintaining a sufficiently accurate Nilometer and record in prehistoric Egypt has caused other scholars to doubt that it formed the basis for the Egyptian calendar.{{sfnp|Parker|1950|p=23}}

Note that the names of the three natural seasons were incorporated into the Civil calendar year (see below), but as this calendar year is a {{nowrap|wandering year}}, the seasons of this calendar slowly rotate through the natural solar year, meaning that Civil season Akhet/Inundation only occasionally coincided with the Nile inundation.

File:2017 Northern Lunar Calendar.png

The Egyptians appear to have used a purely lunar calendar prior to the establishment of the solar civil calendar{{sfnp|Parker|1950|pp=30-32}}{{sfn|Høyrup|p=13}} in which each month began on the morning when the waning crescent moon could no longer be seen.{{sfnp|Parker|1950|p=23}} Until the closing of Egypt's polytheist temples under the Byzantines, the lunar calendar continued to be used as the liturgical year of various cults.{{sfn|Høyrup|p=13}} The lunar calendar divided the month into four weeks, reflecting each quarter of the lunar phases.{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA3 3–4]}} Because the exact time of morning considered to begin the Egyptian day remains uncertain and there is no evidence that any method other than observation was used to determine the beginnings of the lunar months prior to the {{nowrap|4th century BC,{{sfnp|Parker|1950|p=29}}}} there is no sure way to reconstruct exact dates in the lunar calendar from its known dates. The difference between beginning the day at the first light of dawn or at sunrise accounts for an 11–14 year shift in dated observations of the lunar cycle.{{sfnp|O'Mara|2003|p=18}} It remains unknown how the Egyptians dealt with obscurement by clouds when they occurred and the best current algorithms have been shown to differ from actual observation of the waning crescent moon in about one-in-five cases.{{harvp|Schaefer|2000|p=[http://articles.adsabs.harvard.edu/full/gif/2000JHA....31..149S/0000153.000.html 153]–[http://articles.adsabs.harvard.edu/full/gif/2000JHA....31..149S/0000154.000.html 154]}}.

Parker and others have argued for its development into an observational and then calculated lunisolar calendar{{sfnp|Parker|1950|pp=13-29}} which used a 30 day intercalary month every two to three years to accommodate the lunar year's loss of about 11 days a year relative to the solar year and to maintain the placement of the heliacal rising of Sirius within its twelfth month.{{sfnp|Parker|1950|pp=30–32}} No evidence for such a month, however, exists in the present historical record.{{sfnp|Tetley|2014|p=[http://www.egyptchronology.com/uploads/2/6/9/4/26943741/ch_10_resolving_the_eponymous_month_conflict.pdf 153]}}

{{hiero|{{nowrap|Temple Month}}
{{nowrap|Ꜣbd n ḥwt-nṯr{{sfnp|Parker|1950|p=17}}}}|N11:N14-N35-R8-O6|align=left}}

A second lunar calendar is attested by a demotic astronomical papyrus{{cite book |contribution=Papyrus Carlsberg 9 |url=http://pcarlsberg.ku.dk |title=The Papyrus Carlsberg Collection |publisher=University of Copenhagen |location=Copenhagen, DK |access-date=11 February 2017}} dating to sometime after 144 AD which outlines a lunisolar calendar operating in accordance with the Egyptian civil calendar according to a 25 year cycle.{{sfnp|Parker|1950|pp=13–23}} The calendar seems to show its month beginning with the first visibility of the waxing crescent moon, but Parker displayed an error in the cycle of about a day in 500 years,{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA25 25]}} using it to show the cycle was developed to correspond with the new moon around 357{{nbsp}}BC.{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA26 26]}} This date places it prior to the Ptolemaic period and within the native Egyptian Dynasty XXX. Egypt's 1st Persian occupation, however, seems likely to have been its inspiration.{{sfn|Høyrup|p=14}} This lunisolar calendar's calculations apparently continued to be used without correction into the Roman period, even when they no longer precisely matched the observable lunar phases.{{sfnp|Parker|1950|p=27}}

The days of the lunar month — known to the Egyptians as a "temple month"{{sfnp|Parker|1950|p=17}} — were individually named and celebrated as stages in the life of the moon god, variously Thoth in the Middle Kingdom or Khonsu in the Ptolemaic era: "He ... is conceived ... on Psḏntyw; he is born on Ꜣbd; he grows old after Smdt".{{sfnp|Parker|1950|pp=11–12}}

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File:Hubble heic0206j.jpg (bottom) and Orion (right). Together, the three brightest stars of the northern winter sky—Sirius, Betelgeuse (orange star, upper right), and Procyon (upper left)—can also be understood as forming the Winter Triangle.]]

File:Digaonalsternuhr.jpg star chart]]

File:Théodule Devéria (French - (Elephanta Calendar) - Google Art Project.jpg.]]

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{{Further|Sothic cycle}}

The civil calendar was established at some early date in or before the Old Kingdom, with probable evidence of its use early in the reign of Shepseskaf ({{c.|2510}}{{nbsp}}BC, Dynasty IV) and certain attestation during the reign of Neferirkare (mid-25th century{{nbsp}}BC, Dynasty V).{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA28 28]}} It was probably based upon astronomical observations of Sirius{{sfnp|Parker|1950|p=23}} whose reappearance in the sky closely corresponded to the average onset of the Nile flood through the 5th and {{nowrap|4th millennium BC.{{sfnp|Parker|1950|p=32}}}}{{efn|Other possibilities for the original basis of the calendar include comparison of a detailed record of lunar dates against the rising of Sirius over a 40 year span, discounted by Neugebauer as likely to produce a calendar more accurate than the actual one;{{sfnp|Neugebauer|1939}} his own theory (discussed above) that the timing of successive floods were averaged over a few decades;{{sfnp|Neugebauer|1939}} and the theory that the position of the solar rising was recorded over a number of years, permitting comparison of the timing of the solstices over the years. A predynastic petroglyph discovered by the University of South Carolina's expedition at Nekhen in 1986 may preserve such a record, if it had been moved about 10° from its original position prior to discovery.{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA37 37]}}}} A recent development is the discovery that the 30-day month of the Mesopotamian calendar dates as late as the Jemdet Nasr Period (late 4th-millennium{{nbsp}}BC),{{citation |last=Englund |first=Robert K. |contribution=Administrative Timekeeping in Ancient Mesopotamia |title=Journal of the Economic and Social History of the Orient, No. 31 |date=1988 |pages=121–185 }}. a time Egyptian culture was borrowing various objects and cultural features from the Fertile Crescent, leaving open the possibility that the main features of the calendar were borrowed in one direction or the other as well.{{sfn|Høyrup|pp=12–13}}

The civil year comprised exactly 365 days,{{efn|It has been argued that the Ebers Papyrus shows a fixed calendar incorporating leap years, but this is no longer believed.{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA6 6]}}}} divided into 12 months of 30 days each and an intercalary month of five days,{{sfnp|Parker|1950|p=7}} which were celebrated as the birthdays of the gods Osiris, Horus, Set, Isis, and Nephthys.{{sfnp|Spalinger|1995|p=33}} The regular months were grouped into Egypt's three seasons,{{sfnp|Parker|1950|p=7}} which gave them their original names,{{sfnp|Parker|1950|pp=43–5}} and divided into three 10-day periods known as decans or decades. In later sources, these were distinguished as "first", "middle", and "last".{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA4 4]}} It has been suggested that during the Nineteenth Dynasty and the Twentieth Dynasty the last two days of each decan were usually treated as a kind of weekend for the royal craftsmen, with royal artisans free from work.{{sfnp|Jauhiainen|2009|p=39}} Dates were typically expressed in a YMD format, with a pharaoh's regnal year followed by the month followed by the day of the month.{{harvp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA5 5]}}. For example, the New Year occurred on {{nowrap|I Akhet 1.}}

{{hiero|{{nowrap|Lord of Years}}
Nb Rnpt|V30-M4-X1:Z2|align=left}}

The importance of the calendar to Egyptian religion is reflected in the use of the title "Lord of Years" ({{lang|egy|Nb Rnpt}}){{citation |last=Budge |first=Ernest Alfred Wallis |page=[https://books.google.com/books?id=siXEAgAAQBAJ&pg=PA201 201] |title=A Hieroglyphic Vocabulary to the Theban Recension of the Book of the Dead |url=https://books.google.com/books?id=siXEAgAAQBAJ |publisher=Kegan Paul, Trench, Trübner, & Co. |date=1911 |isbn=9780486144924 }}. for its various creator gods.{{harvp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA1 1]}}. Time was also considered an integral aspect of Maat, the cosmic order which opposed chaos, lies, and violence.

The civil calendar was apparently established in a year when Sirius rose on its New Year {{nowrap|(I Akhet 1)}} but, because of its lack of leap years, it began to slowly cycle backwards through the solar year. Sirius itself, about 40° below the ecliptic, follows a Sothic year almost exactly matching that of the Sun, with its reappearance now occurring at the latitude of Cairo (ancient Heliopolis and Memphis) on 19{{nbsp}}July (Julian), only two or three days later than its occurrence in early antiquity.{{sfnp|Parker|1950|p=7}}{{citation |last=Lacroix |first=Jean-Pierre |contribution-url=http://www.ancientcartography.net/LEVERheliaqueAN.html |contribution=Heliacal rising of Sirius in Thebes |title=Thebes: A Reflection of the Sky on the Pharaoh's Earth |url=http://www.ancientcartography.net/index1.html#LINKretour8 |date=1997 }}.

Following Censorinus{{sfnp|O'Mara|2003|p=17}} and Meyer,{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA29 29]}} the standard understanding was that, four years from the calendar's inception, Sirius would have no longer reappeared on the Egyptian New Year but on the next day {{nowrap|(I Akhet 2)}}; four years later, it would have reappeared on the day after that; and so on through the entire calendar until its rise finally returned to {{nowrap|I Akhet 1}} 1460 years after the calendar's inception,{{sfnp|O'Mara|2003|p=17}}{{efn|1460 Julian years (exactly) or Gregorian years (roughly) in modern calculations, equivalent to 1461 Egyptian civil years, but apparently reckoned as 1460 civil years (1459 Julian years) by the ancient Egyptians themselves.{{sfnp|O'Mara|2003|p=17}}}} an event known as "apocatastasis".{{citation |last=Gautschy |first=Rita |title=The Star Sirius in Ancient Egypt and Babylonia |url=http://www.gautschy.ch/~rita/archast/sirius/siriuseng.htm |date=2012 }}. Owing to the event's extreme regularity, Egyptian recordings of the calendrical date of the rise of Sirius have been used by Egyptologists to fix its calendar and other events dated to it, at least to the level of the four-Egyptian-year periods which share the same date for Sirius's return, known as "tetraëterides" or "quadrennia". For example, an account that Sothis rose on {{nowrap|III Peret 1}}—the 181st day of the year—should show that somewhere 720, 721, 722, or 723 years have passed since the last apocatastasis.{{sfnp|O'Mara|2003|p=17}} Following such a scheme, the record of Sirius rising on {{nowrap|II Shemu 1}} in 239{{nbsp}}BC implies apocatastases on 1319 and 2779{{nbsp}}BC ±3 years.{{sfnp|O'Mara|2003|p=18}}{{efn|Per O'Mara, actually ±16 years when including the other factors affecting the calculated Sothic year.{{sfnp|O'Mara|2003|p=18}}}} Censorinus's placement of an apocatastasis on 21{{nbsp}}July AD{{nbsp}}139{{efn|Using Roman dating, he said of the relevant New Year that "when the emperor Antoninus Pius was consul of Rome for a second time with Bruttius Praesens this same day coincided with the 13th day before the calends of August" ({{langx|la|cum... imperatore quinque hoc anno fuit Antonino Pio II Bruttio Praesente Romae consulibus idem dies fuerit ante diem XII kal. Aug.}}).{{citation |author=Censorinus |author-link=Censorinus |title=De Die Natali |year=1867 |publisher=Lipsia, Teubner |url=https://archive.org/stream/dedienataliliber00cens |at=[https://archive.org/stream/dedienataliliber00cens#page/46/mode/2up Ch. XXI, §10] |language=la}}, [http://elfinspell.com/ClassicalTexts/Maude/Censorinus/DeDieNatale-Part2.html#topref93 translated into English] by William Maude in 1900.}} permitted the calculation of its predecessors to 1322, 2782, and 4242{{nbsp}}BC.{{Failed verification|date=September 2019|reason=The article doesn't mention these years, and makes no mention of Censorinus}} The last is sometimes described as "the first exactly dated year in history"{{citation |last=Grun |first=Bernard |author-link=Bernard Grun |title=The Timetables of History, 3rd ed. |contribution=4241{{nbsp}}BC |date=1975 |publisher=Thames & Hudson }}. but, since the calendar is attested before Dynasty XVIII and the last date is now known to far predate early Egyptian civilization, it is typically credited to Dynasty II around the middle date.{{efn|Meyer himself accepted the earliest date,{{harvp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA31 31]}}. though before the Middle Chronology was shown to be more likely than the short or long chronologies of the Middle East. Parker argued for its introduction ahead of apocatastasis on the middle date based on his understanding of its development from a Sothic-based lunar calendar. He placed its introduction within the range {{c.|2937|2821}}{{nbsp}}BC, noting it was more likely in the Dynasty II part of the range.{{sfnp|Parker|1950|p=53}}{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA36 36–7]}}}}

The classic understanding of the Sothic cycle relies, however, on several potentially erroneous assumptions. Following Scaliger,{{citation |last=Scaliger |first=Joseph Justus |author-link=Joseph Justus Scaliger |title=Opus Novum de Emendatione Temporum |date=1583 |page=138 }}. {{in lang|la}} Censorinus's date is usually emended to 20{{nbsp}}July{{efn|{{langx|la|...ante diem XIII kal. Aug....{{sfnp|Grafton & al.|1985|p=455}}}}}} but ancient authorities give a variety of 'fixed' dates for the rise of Sirius.{{efn|Most ancient sources place the heliacal rising of Sirius on 19{{nbsp}}July, but Dositheus, probable source of the date of the 239{{nbsp}}BC rising, elsewhere places it on 18{{nbsp}}July,{{sfnp|O'Mara|2003|p=18}} as do Hephaistion of Thebes,{{sfnp|Luft|2006|p=314}} Salmasius, Zoroaster, Palladius, and Aëtius. Solinus placed it on the 20th; Meton and the unemended text of Censorinus's book on the 21st; and Ptolemy on the day after that.{{sfnp|O'Mara|2003|p=18}}}} His use of the year 139 seems questionable,{{sfnp|O'Mara|2003|p=25}} as 136 seems to have been the start of the tetraëteris{{sfnp|Luft|2006|p=312}} and the later date chosen to flatter the birthday of Censorinus's patron.{{sfnp|Forisek|2003|p=12}} Perfect observation of Sirius's actual behavior during the cycle—including its minor shift relative to the solar year—would produce a period of 1457 years; observational difficulties produce a further margin of error of about two decades. Although it is certain the Egyptian day began in the morning, another four years are shifted depending on whether the precise start occurred at the first light of dawn or at sunrise.{{sfnp|O'Mara|2003|p=18}} It has been noted that there is no recognition in surviving records that Sirius's minor irregularities sometimes produce a triëteris or penteteris (three- or five-year periods of agreement with an Egyptian date) rather than the usual four-year periods and, given that the expected discrepancy is no more than 8 years in 1460, the cycle may have been applied schematically{{sfnp|Clagett|1995|p=[https://books.google.com/books?id=xKKPUpDOTKAC&pg=PA30 30]}} according to the civil years by Egyptians and the Julian year by the Greeks and Romans.{{sfnp|O'Mara|2003|p=17}} The occurrence of the apocatastasis in the {{nowrap|2nd millennium BC}} so close to the great political and sun-based religious reforms of {{nowrap|Amenhotep IV}}/Akhenaton also leaves open the possibility that the cycle's strict application was occasionally subject to political interference.{{sfnp|Schaefer|2000|p=[http://articles.adsabs.harvard.edu/full/gif/2000JHA....31..149S/0000152.000.html 152]–[http://articles.adsabs.harvard.edu/full/gif/2000JHA....31..149S/0000153.000.html 3]}} The record and celebration of Sirius's rising would also vary by several days (equating to decades of the cycle) in eras when the official site of observation was moved from near Cairo.{{efn|This seems to be the case, for example, with astronomical records of the XVIII Dynasty and its successors, including the Ebers Papyrus, which seem to have been made at Thebes rather than Heliopolis.{{citation |contribution=Ancient Egyptian Civil Calendar |contribution-url=http://www.lavia.org/english/archivo/egyptiancalendaren.html |publisher=La Via |title=Biblical Archaeology |url=http://www.lavia.org/english/archivo/index_en.htm }}.}} The return of Sirius to the night sky varies by about a day per degree of latitude, causing it to be seen 8–10 days earlier at Aswan than at Alexandria,{{sfnp|Tetley|2014|p=[http://www.egyptchronology.com/uploads/2/6/9/4/26943741/ch_3_investigating_ancient_egyptian_calendars.pdf 43]}} a difference which causes Rolf Krauss to propose dating much of Egyptian history decades later than the present consensus.

Following Alexander the Great's conquest of the Persian Empire, the Macedonian Ptolemaic Dynasty came to power in Egypt, continuing to use its native calendars with Hellenized names. In 238 BC, Ptolemy III's Canopus Decree ordered that every 4th year should incorporate a sixth day in its intercalary month,[https://www.trismegistos.org/downloads/process.php?file=TOP_1.pdf A Chronological Survey of Precisely Dated Demotic and Abnormal Hieratic Sources] honoring him and his wife as gods equivalent to the children of Nut. The reform was resisted by the Egyptian priests and people and was abandoned.

{{main|Coptic calendar}}

Egyptian scholars were involved with the establishment of Julius Caesar's reform of the Roman calendar, although the Roman priests initially misapplied its formula and—by counting inclusively—added leap days every three years instead of every four. The mistake was corrected by Augustus through omitting leap years for a number of cycles until AD{{nbsp}}4. As the personal ruler of Egypt, he also imposed a reform of its calendar in 26 or 25{{nbsp}}BC, possibly to correspond with the beginning of a new Callipic cycle, with the first leap day occurring on 6 Epag. in the year 22{{nbsp}}BC. This "Alexandrian calendar" corresponds almost exactly to the Julian, causing 1{{nbsp}}Thoth to remain at 29{{nbsp}}August except during the year before a Julian leap year, when it occurs on 30{{nbsp}}August instead. The calendars then resume their correspondence after 4{{nbsp}}Phamenoth{{nbsp}}/ 29{{nbsp}}February of the next year.[http://www.tyndalehouse.com/Egypt/ptolemies/chron/egyptian/chron_eg_anl_augustus.htm Alexandrian reform of the Egyptian calendar]

For much of Egyptian history, the months were not referred to by individual names, but were rather numbered within the three seasons.{{sfnp|Parker|1950|pp=43–5}} As early as the Middle Kingdom, however, each month had its own name. These finally evolved into the New Kingdom months, which in turn gave rise to the Hellenized names that were used for chronology by Ptolemy in his Almagest and by others. Copernicus constructed his tables for the motion of the planets based on the Egyptian year because of its mathematical regularity. A convention of modern Egyptologists is to number the months consecutively using Roman numerals.

A persistent problem of Egyptology has been that the festivals which give their names to the months occur in the next month. Alan Gardiner proposed that an original calendar governed by the priests of Ra was supplanted by an improvement developed by the partisans of Thoth. Parker connected the discrepancy to his theories concerning the lunar calendar. Sethe, Weill, and Clagett proposed that the names expressed the idea that each month culminated in the festival beginning the next.{{sfnp|Clagett|1995|p=14–15}}

Calendars that have survived from ancient Egypt often characterise the days as either lucky or unlucky. Of the calendars recovered, the Cairo calendar is one of the best examples. Discovered in modern-day Thebes, it dates from the Ramesside Period and acts as a guide to which days were considered lucky or unlucky. Other complete calendars include Papyrus Sallier IV,{{cite web |title=papyrus; calendar |url=https://www.britishmuseum.org/collection/object/Y_EA10184-7 |website=The British Museum}} and the Calendar of Lucky and Unlucky Days (on the back of the Teaching of Amenemope).{{cite web |title=papyrus |url=https://www.britishmuseum.org/collection/object/Y_EA10474-1 |website=The British Museum}} The earliest calendars appear in the Middle Kingdom, but they do not become codified until the New Kingdom. It is unknown how staunchly these calendars were adhered to, as there are no references to decisions being made based on their horoscopes. Nevertheless, the different copies of the calendars are remarkably consistent with each other, with only 9.2% of the determinations of adversity or fortuitousness being due to a defined textual reason.{{cite thesis |last1=Leaning |first1=Elizabeth |title=Searching the Years: Religion and Superstition in ancient Egypt as Seen Through Horoscopes |date=2022 |page=20 |publisher=ResearchSpace@Auckland |hdl=2292/64494 |url=https://hdl.handle.net/2292/64494|type=Thesis }}

The Calendars of Lucky and Unlucky Days seem to be based on scientific observation as well as myths. Periodicity has been established between phases of the moon as well as the brightening and dimming of the three-star system Algol as visible from earth.{{cite journal |last1=Porceddu |first1=Sebastian |last2=Jetsu |first2=Lauri |last3=Markkanen |first3=Tapio |last4=Toivari-Viitala |first4=Jaana |title=Evidence of Periodicity in Ancient Egyptian Calendars of Lucky and Unlucky Days |journal=Cambridge Archaeological Journal |date=2008 |volume=18 |issue=3 |pages=327–339 |doi=10.1017/S0959774308000395|bibcode=2008CArcJ..18..327P |url=https://zenodo.org/record/896419 }}

The calendars could also be used to predict someone's future depending on the day they were born. This could also be used to predict when or how they would die. For example, people born on the tenth day of the fourth month of Akhet were predicted to die of old age.{{Cite book |last=Gahlin |first=Lucia |title=Egypt Gods, myths and religion |publisher=Hermes House |year=2014 |isbn=978-0-85723-123-9 |pages=216–217}}

The epagomenal days were added to the original 360 day calendar in order to synchronise the calendar with the approximate length of the solar year. Mythologically, these days allowed for the births of five children of Geb and Nut to occur and were considered to be particularly dangerous. In particular, the day Seth was supposed to be born was considered particularly evil.{{Cite book |last=Riggs |first=Christina |title=Ancient Egyptian magic a hands-on guide |publisher=Thames & Hudson |year=2020 |isbn=978-0-500-05212-9 |pages=167}}

File:Calendar Icon Sinai 11th century.jpg calendrical icon displaying two months of saints, by John Tokhabi.]]

{{main|Coptic calendar|Ethiopian calendar}}

The reformed Egyptian calendar continues to be used in Egypt as the Coptic calendar of the Egyptian Church and by the Egyptian populace at large, particularly the fellah, to calculate the agricultural seasons. It differs only in its era, which is dated from the ascension of the Roman emperor Diocletian. Contemporary Egyptian farmers, like their ancient predecessors, divide the year into three seasons: winter, summer, and inundation.

The Ethiopian calendar is based on this reformed calendar but uses Amharic names for its months and uses a different era. The French Republican Calendar was similar, but began its year at the autumnal equinox. British orrery maker John Gleave represented the Egyptian calendar in a reconstruction of the Antikythera mechanism.

• Egyptian chronology
• Egyptian astronomy
• Egyptian days

{{Notelist}}

{{Reflist|30em}}

• {{citation |first=James P. |last=Allen |author-link=James Peter Allen |title=Middle Egyptian: An Introduction to the Language and Culture of Hieroglyphs, Third Edition |year=2014 |location=Cambridge |publisher=Cambridge University Press |isbn=978-1-107-66328-2}}.
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• [http://www.instonebrewer.com/TyndaleSites/Egypt/ptolemies/chron/egyptian/chron_eg_intro.htm Detailed information about the Egyptian calendars, including lunar cycles]
• [http://egypt.online-resourcen.de/content/Date-Converter-Ancient-Egypt Date Converter for Ancient Egypt]
• [https://web.archive.org/web/20050216102054/http://emr.cs.iit.edu/home/reingold/calendar-book/Calendrica.html Calendrica] Includes the Egyptian civil calendar with years in Ptolemy's Nabonassar Era (year 1 = 747 BC) as well as the Coptic, Ethiopic, and French calendars.
• [http://www.egyptologyforum.org/civil4.0.zip Civil, ver. 4.0], is a 25kB DOS program to convert dates in the Egyptian civil calendar to the Julian or Gregorian ones

{{Calendars}}

{{Ancient Egypt topics}}

{{Authority control}}

Category:30th-century BC establishments

Category:Solar calendars

Category:Ancient calendars