The Origins of Egyptian Calendars and Their Modern Legacy

Dr. Ronald Wells, currently a computer resource specialist at the University of California, Berkeley, and an astronomer who studied ancient Egyptian grammar and history at the Near Eastern Studies Department in Berkeley in the 70s compared his return to speak to that department and the members of ARCE to the return of Sinuhe from his self-exile in Palestine. He began his January talk noting that the need to measure time was of vital interest to humankind. Knowing when to plant and when to harvest are necessary to the success of food production. Dr. Wells recom-mended consulting Revolutions in Time: Studies in Ancient Egyptian Calendrics, a compendium of essays on ancient timekeeping published by Van Siclen Books as a good starting point for studying the development of ancient time measurement. Alternatively, his chapter on the same subject can also be found in Astronomy Before the Telescope published by the British Museum Press in 1996.

Showing a Landsat image of northeastern Africa, Dr. Wells pointed to the differences between the Delta and the Valley of the Nile in terms of the environment and the arable land available. These differences contributed to the development of the notion of duality which dominated ancient Egyptian thought and religion.

Religion in the north had its focus on solar imagery (the pyramids at Giza and the sun temples at Abu Ghurab, for example) while in the south the emphasis was mainly stellar in origin (embodied by the temple of Satet at Elephantine). The earliest calendars in use in Egypt appear to be lunar in origin, based on phases of the moon. Such calendars were used to determine festival dates in the religious year. In the south the main festival was the ÔGoing ForthÕ of the star Sirius (Prt Spdt); while in the north the `Birth of the SunÕ (Mswt Rc) was the chief festival of interest; each occurs roughly six lunar phases apart.

The legend of the Goddess Nut (as depicted on the ceilings of a variety of temples and tombs, e.g., the tomb of Rameses VI in the Valley of the Kings) holds the key to some of the astronomical observations which combined to form the Egyptian year. The Rameses VI ceiling has mirrored images of Nut (her body running back-to-back in Siamese twin fashion in an East/West orientation along the center of the vaulted ceiling of the tomb) with her limbs outstretched and dropping down to the north and south walls (one twin represents the northern, the other, the southern half of the sky). The southern facing Nut has ten solar disks running along her body, as well as one at her mouth and another one at the birth canal between her legs painted with the image of Khepri (the god of coming into being). No disks are depicted on the northern facing Nut because the sun is always seen to traverse the southern part of the sky in Egypt. The stars on NutÕs body represent the brightest stars of the Milky Way, the latter of which gives the impression of a diaphanous gown cloaking a female body. The stars of the constellation Cygnus mark a bifurcation of the Milky Way into leg-like appendages, the brightest star Deneb ( Cyg) located at the position of the birth canal. The Barque of Re traverses her body as the sun passes through the heavens. The ecliptic passes through the mouth of the head of Nut as formed by the Milky Way near the constellation of Gemini. About an hour and a half after sunset on the Vernal (Spring) Equinox near Cairo around 3500 B.C.E. a glimmering head, face-up with mouth agape, would have been seen on the western horizon at the point where the sun had disappeared. Nine months later at the Winter Solstice the sun appears on the horizon at sunrise as though dropped directly from Deneb in Cygnus, very much like GardinerÕs Sign-List glyph B3, the squatting female giving birth. That is, on a hemispherical projection of the sky, a line connecting the North Celestial Pole (about which the ÔUndying StarsÕ rotate), Deneb, and the horizon sunrise point all form a great circle at this one moment each year. The imagery of the sun coursing through the body of Nut to give birth to himself once each year was later used by the Kings of Egypt to herald their divine birth as Sons of Re. Re in the guise of the pharaoh was sup-posed to impregnate the queen to produce the next generation (this legend is the origin of the matrilineal inheritance of the Egyptian throne). Observations of this phenomenon point to a date somewhat earlier, around 4500 B.C.E., for the origins of the mythology of Nut. The importance that the Egyptians placed on this annual birthday event (Mswt Rc) motivated the development of the first religious calendar. Although 365 days could be counted between each occurrence, it would have been noticed that twelve phases of the moon almost coincided with the same interval. However, since a lunar year averages only 354 days, the next yearÕs birthday festival would not fall on the same day of the last month. Eventually in two or three years, the birthday would fall out of the last month altogether. Since the month was named for the major festival being celebrated in it, this situation could only be avoided by the periodic intercalation of a whole month of 30 days at the beginning of the year to force the celebration back into the last month (a little math shows that whenever the first day of a new year occurred within 11 days after a winter solstice feast, then the new year would have to contain the intercalary 13th month placed at its beginning). Intercalation did not restore the event to the same day of the month, but at least it kept the celebration within the correctly named month. In Upper Egypt, a temple was built at Elephantine Island at Aswan (believed to be the wellspring source of the Nile) dedicated to the goddess Satet (Sothis in Greek = Sirius). A view down the axis of this temple marks the winter solstice sunrise and also (with allowance for the knoll across the river) permits a view of the star Sirius as it rises above the horizon. The special annual rising of Sirius (or ÔGoing Forth of SiriusÕ, Prt Spdt) just before sunrise (heliacal rising in astronomical terminology) near the time of the summer solstice also marked the rise of the Nile floodwaters as measured by the Nilometer at Aswan. This appearance before the sun occurs after a seventy day absence from the sky, a period which also became the duration of interment of later pharaohs.

Observations of this phenomenon also point to a date around 4500 B.C.E. for the origins of another Egyptian lunar calendar in Upper Egypt having come into being like that in the North, except that its chief festival celebrated the rise of Sirius and the Nile. The star Sirius is also equated with Isis who is the daughter of Re. These two festivals of the North and South (Mswt Rc and Prt Spdt) occur about six months apart. The Egyptian lunar calendar of the pharaonic period begins with Prt Spdt and has a 12th month called Mswt Rc which was apparently a combination of both predynastic calendars, a result of the union of the North and the South. The first day of each new year on which Sirius rose heliacally was also called Wp Rnpt (Opener of the Year). The first hieroglyph in the word wp is a pair of ox horns and this same symbol forms part of the crown of the goddess Satet as seen on her temple at Elephantine.

The priests who regulated the calendars were given the title ÔOverseers of the HoursÕ. In the first dynasties as writing spread through the country, the lunar religious calendar was simplified to twelve months of thirty days with five days added to the beginning because the religious calendar was too cumbersome to use for commercial transactions. This new calendar is called the civil calendar and is the earliest form of our modern western counterpart. Because the year is actually about a quarter of a day longer than this averaged civil year it gradually goes out of synchron-ization with the observable festival year and so both the lunar and religious calendars were used side by side throughout Egyptian history. The development of the hour also grew out of the need to provide for religious rites to occur at their proper time (at actual sunrise on any given day, for example). The sungod Re traverses the netherworld where he is confronted by demons and demigods who attempt to impede his progress to be reborn at sunrise. Spells found in the Valley of the Kings (the Book of Gates, for example) help Re pass through twelve portals or hours of the night. Re had to recite the names of each Gate, Gate Keeper, and his assistant demigods in order to pass safely to the next one. Dr. Wells pointed out that the Book of Gates was simply a mnemonic device ensuring that the proper sequence of constellations which came out of the Underworld would be remembered correctly (i.e., the recitations at each Gate). It would work to measure hours in the following manner.

Observations of a single star show that it rises four minutes later each day so that in the ideal case observations of twenty-four stars equally spaced across the sky would be needed to make accurate predictions of sunrise throughout the year in which a given star would be used to mark the hour before sunrise. That star could serve as a ÔHeraldÕ for only 15 days before it rose 2 hours before sunrise and thus had to be replaced by the next star in the series. Since it would be difficult to recognize which bright stars were which rising near the same place on the horizon, star groups or patterns of stars surrounding the brighter star would be needed to aid recognition. The brightest star of a particular group represents the Gate Keeper. The other fainter stars in the pattern, or constellation, are the attendants or demigods. The place on the horizon where they rose would be the Gate itself. Writing down the names of all these deities and the stories associated with them thus became the Book of Gates. The usual number is 12 gates, corresponding to the 12 hours of night, but variants with eight or ten gates also are known to exist. These would simply represent star clocks with 8 or 10 constellations used to predict sunrise.

At Abusir and Abu Ghurab are the remains of two of six known sun temples that were built during the Old Kingdom 5th Dynasty. The alabaster altar of NiuserreÕs sun temple is still in place (although Dr. Wells argues that it should be removed to the Cairo Museum and saved from further damage with a substitute placed in situ) which is formed from four hotep signs oriented towards the cardinal directions and surrounding a large solar disk. The altar therefore actually says ÔRe is satisfiedÕ in the four principal directions. Dr. Wells believes that the lower valley temple roof located in the priestsÕ village below each sun temple, which was situated higher up on a small hillock, could have been used to make stellar observations used in calculating the hours of night in the manner described above.

Deneb (the birth star of Re in Cygnus) was part of the series of stars found to rise along the axis of the lower temple belonging to the sun temple of Userkaf, the first of the six that were built. Although these stars rose on average about an hour apart, the actual inter-vals between star rises were quite variable indicating that the first hours to be measured were of unequal length. Different interval (or ÔhourÕ) lengths were used at the different temples because their valley temples faced different sets of rising stars.

As determined from the coffin lids of the 8th-10th Dynasties, a new type of hour was introduced during the period between the Old and Middle Kingdoms. It was called the decanal hour based on a group of stars similar to Sirius in that they were absent from the sky for 70 days. The decanal hour was 40 minutes in length based upon sets of thirty-six such stars (the Dendera star ceiling, a much later example) which marked a given hour for 10 days (not 15) before being replaced by the next in the series. Eighteen stars would be observable above the horizon while eighteen remained below. Three of the 18 denoted the twilight hours before sunrise and another three again after sunset so that you would get twelve hours of darkness (18 x 40 min/60 min = 12).

Calendars of lucky days and unlucky days also are known from Deir El Medina and elsewhere. These were days portending evil or good fortune for people born on a particular day. The civil calendar was standardized into a 365 day year with the division of the night and day into twelve hours each which was handed down to us through the Greeks and Romans. Dr. Wells ended his talk by illustrating with a few slides the two most important uses of the ability to measure the hour length handed down to us by the ancient Egyptians: the measurement of longitude at sea which depends on a very precise chronometer to measure the hour; and the landing of men on the moon which also required precision measurement of time. He noted the coincidence of the Apollo missions and the television show Star Trek each lasting approximately the same three years with only Star Trek having continued on with new missions and crews. He hoped that new explorations of the moon, the source of our time keeping, might begin again.

  • Al Berens as corrected by Ronald Wells
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