Egyptian calendar

thumb|right|200px|A section of the [[Egyptian hieroglyphs|hieroglyphic calendar at the Kom Ombo Temple, displaying the transition from Month XII to Month I without mention of the five epagomenal days.]]

thumb|right|200px|[[Astronomical ceiling of Senenmut's Tomb|Astronomical ceiling from the Tomb of Senenmut (XVIII Dynasty, –1458 BC), discovered in Thebes, Upper Egypt; facsimile preserved in the Metropolitan Museum of Art.]]

thumb|right|200px|The [[sky goddess Nut and human figures representing stars and constellations from the star chart in the tomb of Ramses VI.]]

The ancient Egyptian calendar a civil calendar was a solar calendar with a 365-day year. The year consisted of three seasons of 120 days each, plus a short intercalary 'month' of five epagomenal days that was treated as outside of the year proper. Each season was divided into four months of 30 days. These twelve months were initially numbered within each season but came to also be known by the names of their principal festivals. Each month was divided into three 10-day periods known as decans or decades. 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.

Because this calendrical year was nearly a quarter of a day shorter than the solar year and did not have any leap years, the Egyptian calendar lost about one day every four years relative to the Julian calendar. It is therefore sometimes referred to as the (), as its months rotated about one day through the solar year every four years. 's Canopus Decree attempted to correct this through the introduction of a sixth epagomenal day every four years but the proposal was resisted by the Egyptian priests and people and abandoned until the decree by Augustus in 25BC that established the Alexandrian or Coptic calendar. The introduction of a leap day to the Egyptian calendar made it equivalent to the Julian calendar, although (like the latter) it continues to diverge from the Gregorian calendar at the turn of most centuries.

This ran concurrently with an Egyptian lunar calendar which was used for some religious rituals and festivals.

History

Prehistory

thumb|right|200px|The Nile flood at [[Cairo .]]

Current understanding of the earliest development of the Egyptian calendar remains speculative. A tablet from the reign of the First Dynasty pharaoh Djer (BC) was once thought to indicate that the Egyptians had already established a link between the heliacal rising of Sirius ( or Sopdet, "Triangle"; , Sôthis) and the beginning of their year, but more recent analysis has questioned whether the tablet's picture refers to Sirius at all. 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. Some evidence suggests the early civil calendar had 360 days, 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, ancient Egypt was "a gift of the river" Nile, whose annual flooding organized the natural year into three broad natural seasons known to the Egyptians as:

Inundation or Flood (, sometimes anglicized as Akhet): roughly from September to January.
Emergence or Winter (', sometimes anglicized as Peret): roughly from January to May.
Low Water or Harvest or Summer (', sometimes anglicized as Shemu): roughly from May to September.

Parker and others have argued for its development into an observational and then calculated lunisolar calendar 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. No evidence for such a month, however, exists in the present historical record.

A second lunar calendar is attested by a demotic astronomical papyrus 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. 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, using it to show the cycle was developed to correspond with the new moon around 357BC. 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. 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.

The days of the lunar month — known to the Egyptians as a "temple month" — 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".

{| class="wikitable" style="margin:1em auto;"

|+ Days of the lunar month

! rowspan=2 | Day

! colspan=3 | Name

! colspan=2 | Egyptian

! Meaning (if known)

| align="center" | 1

| align="center" | <hiero>N10-G4-W3</hiero> || Psḏtyw || Literal meaning unknown but possibly related to the Ennead; the day of the New Moon.

| align="center" | 2

| align="center" | <hiero>D1-N11:N14</hiero> || Tp Ꜣbd Ꜣbd || "Beginning the Month" or "The Month"; the beginning of the Crescent Moon.

| align="center" | 3

| align="center" | <hiero>F31-Q3:D21-W3</hiero> || Mspr || "Arrival"

| align="center" | 4

| align="center" | <hiero>O1:D21-X1-S29-G17-W3</hiero> || Prt Sm || "The Going Forth of the Sm", a kind of priest

| align="center" | 5

| align="center" | <hiero>Aa1:X1-D2:Z1-R2-W3</hiero> || I͗ḫt Ḥr Ḫꜣwt || "Offerings upon the Altar"

| align="center" | 6

| align="center" | <hiero>S29-T22-N35:X1-Z2:Z2-W3</hiero> || Snt || "The Sixth"

| align="center" | 7

| align="center" | <hiero>D46:N35-M17-X1-W3</hiero> || Dnı͗t || "Partial"; the first-quarter day.

| align="center" | 8

| align="center" | <hiero>D1*D12:W3</hiero> || Tp || Unknown

| align="center" | 9

| align="center" | <hiero>F19-Q3:W3</hiero> || Kꜣp || Unknown

| align="center" | 10

| align="center" | <hiero>S29-M17-I9:D52-W3</hiero> || Sı͗f || Unknown

| align="center" | 11

| align="center" | <hiero>F29-N8-Z2:W3</hiero> || Stt || Unknown

| align="center" | 12

| align="center" | <hiero>N31:D53-N31:D53-W3</hiero> || Unknown || "Partial" the second-quarter day.

| align="center" | 13

| align="center" | <hiero>D12-D12-U1-A59-W3</hiero> || Mꜣꜣ Sṯy || Unknown

| align="center" | 14

| align="center" | <hiero>S32-G1-Z7-W3</hiero> || Sı͗ꜣw || Unknown

| align="center" | 15

| align="center" | <hiero>D1-N13</hiero> || Smdt Tp Smdt || Literal meaning uncertain; the day of the Full Moon.

| align="center" | 16

| align="center" | <hiero>F31-Q3:D21-Z1*Z1:W24-W3</hiero> || Mspr Sn Nw Ḥbs Tp || "Second Arrival" "Covering the Head"

| align="center" | 17

| align="center" | <hiero>S32-G1-Z7-W3</hiero> || Sı͗ꜣw || Second Quarter Day

| align="center" | 18

| align="center" | <hiero>M17-V28-N12-W3</hiero> || I͗ꜥḥ || "Day of the Moon"

| align="center" | 19

| align="center" | <hiero>F21-S43-S43-S43-I9:W3</hiero> || Sḏm Mdwf || Unknown

| align="center" | 20

| align="center" | <hiero>U21:Q3-W3</hiero> || Stp || Unknown

| align="center" | 21

| align="center" | <hiero>Aa20-D21:G43-W3</hiero> || Ꜥprw || Unknown

| align="center" | 22

| align="center" | <hiero>F22-M44-X1:W3</hiero> || Pḥ Spdt || Unknown

| align="center" | 23

| align="center" | <hiero>D46:N35-M17-X1:V11-W3</hiero> || Dnı͗t || "Partial"; the third-quarter day.

| align="center" | 24

| align="center" | <hiero>V31:N35-V28-G43-N2-W3</hiero> || Knḥw || Unknown

| align="center" | 25

| align="center" | <hiero>F29-N8-Z2:W3</hiero> || Stt || Unknown

| align="center" | 26

| align="center" | <hiero>O1:D21-X1:W3</hiero> || Prt || "The Going Forth"

| align="center" | 27

| align="center" | <hiero>G43-N37-D58-W3</hiero> || Wšb || Unknown

| align="center" | 28

| align="center" | <hiero>O23-W24*X1:N1-W3</hiero> || Ḥb Sd Nwt || "The Jubilee of Nut"

| align="center" | 29

| align="center" | <hiero>P6-A47-W3</hiero> || Ꜥḥꜥ || Unknown

| align="center" | 30

| align="center" | <hiero>O1:D21-X1:D54-O34:R12:X1*Z4-W3</hiero> || Prt Mn || "The Going Forth of Min"

Civil calendar

thumb|right|200px|[[Sirius (star)|Sirius (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.]]

thumb|200px|A [[Middle Kingdom of Egypt|Middle Kingdom star chart]]

thumb|right|200px|A hieroglyphic calendar at [[Elephantine.]]

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 (BC, Dynasty IV) and certain attestation during the reign of Neferirkare (mid-25th centuryBC, Dynasty V). It was probably based upon astronomical observations of Sirius whose reappearance in the sky closely corresponded to the average onset of the Nile flood through the 5th and 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-millenniumBC), 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.

The civil year comprised exactly 365 days, divided into 12 months of 30 days each and an intercalary month of five days, which were celebrated as the birthdays of the gods Osiris, Horus, Set, Isis, and Nephthys. The regular months were grouped into Egypt's three seasons, which gave them their original names, and divided into three 10-day periods known as decans or decades. In later sources, these were distinguished as "first", "middle", and "last". 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. 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. For example, the New Year occurred on

The importance of the calendar to Egyptian religion is reflected in the use of the title "Lord of Years" (') for its various creator gods. Time was also considered an integral aspect of Maat,

Following Censorinus and Meyer, 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 ; 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 1460 years after the calendar's inception, an event known as "apocatastasis". 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". permitted the calculation of its predecessors to 1322, 2782, and 4242BC. 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. 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 BC, noting it was more likely in the Dynasty II part of the range.

{| class="wikitable" style="margin:1em auto;"

|+ Heliacal rising of Sirius at Heliopolis

! rowspan=2 | Year

! colspan=3 | Date

! Egyptian !! Julian !! Gregorian

|- align="center"

| 3500BC || || July 16 || June 18

|- align="center"

| 3000BC || || July 16 || June 22

|- align="center"

| 2500BC || III Akhet 8 || July 16 || June 26

|- align="center"

| 2000BC || III Peret 14 || July 17 || June 30

|- align="center"

| 1500BC || III Shemu 19 || July 17 || July 4

|- align="center"

| 1000BC || III Akhet 19 || July 17 || July 8

|- align="center"

|   500BC || III Peret 25 || July 18 || July 13

|- align="center"

| AD1    || III Shemu 30 || July 18 || July 16

|- align="center"

| AD500 || IV Akhet 2 || July 20 || July 22

The classic understanding of the Sothic cycle relies, however, on several potentially erroneous assumptions. Following Scaliger, Censorinus's date is usually emended to 20July but ancient authorities give a variety of 'fixed' dates for the rise of Sirius. His use of the year 139 seems questionable, as 136 seems to have been the start of the tetraëteris and the later date chosen to flatter the birthday of Censorinus's patron. 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. 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, a difference which causes Rolf Krauss to propose dating much of Egyptian history decades later than the present consensus.

Ptolemaic calendar

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, 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.

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 AD4. As the personal ruler of Egypt, he also imposed a reform of its calendar in 26 or 25BC, possibly to correspond with the beginning of a new Callipic cycle, with the first leap day occurring on 6 Epag. in the year 22BC. This "Alexandrian calendar" corresponds almost exactly to the Julian, causing 1Thoth to remain at 29August except during the year before a Julian leap year, when it occurs on 30August instead. The calendars then resume their correspondence after 4Phamenoth/ 29February of the next year.

Months

For much of Egyptian history, the months were not referred to by individual names, but were rather numbered within the three seasons. 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.

{| class="wikitable"

|+ Months

!rowspan=2|Egyptological

!rowspan=2|English

!rowspan=2; colspan=2 |Coptic

!Seasonal || Phaōphí || || Baôba

| align="center" | III || III Akhet Athyr || 3rd Month of Flood 3 Ꜣḫt || Ḥwt-ḥwr || <hiero>O6-t:O1-Hr:r-I12</hiero> Ḥwt-ḥr(w) || || Athúr || || Hatûr

| align="center" | IV || IV Akhet Choiak || 4th Month of Flood 4 Ꜣḫt || KꜢ-ḥr-KꜢ || <hiero>kA-Hr:Z1-kA</hiero> KꜢ-ḥr-KꜢ ||