Ancient Egypt, The Egyptian calendar
Robert Guisepi, 1984
The Valley of the Nile
ancient Egyptians originally employed a calendar based upon the Moon, and,
like many peoples throughout the world, they regulated their lunar calendar
by means of the guidance of a sidereal calendar. They used the seasonal
appearance of the star Sirius (Sothis); this corresponded closely to the
true solar year, being only 12 minutes shorter. Certain difficulties arose,
however, because of the inherent incompatibility of lunar and solar years.
To solve this problem the Egyptians invented a schematized civil year of 365
days divided into three seasons, each of which consisted of four months of
30 days each. To complete the year, five intercalary days were added at its
end, so that the 12 months were equal to 360 days plus five extra days. This
civil calendar was derived from the lunar calendar (using months) and the
agricultural, or Nile, fluctuations (using seasons); it was, however, no
longer directly connected to either and thus was not controlled by them. The
civil calendar served government and administration, while the lunar
calendar continued to regulate religious affairs and everyday life.
time, the discrepancy between the civil calendar and the older lunar
structure became obvious. Because the lunar calendar was controlled by the
rising of Sirius, its months would correspond to the same season each year,
while the civil calendar would move through the seasons because the civil
year was about one-fourth day shorter than the solar year. Hence, every four
years it would fall behind the solar year by one day, and after 1,460 years
it would again agree with the lunisolar calendar. Such a period of time is
called a Sothic cycle.
Because of the discrepancy between these two calendars, the Egyptians
established a second lunar calendar based upon the civil year and not, as
the older one had been, upon the sighting of Sirius. It was schematic and
artificial, and its purpose was to determine religious celebrations and
duties. In order to keep it in general agreement with the civil year, a
month was intercalated every time the first day of the lunar year came
before the first day of the civil year; later, a 25-year cycle of
intercalation was introduced. The original lunar calendar, however, was not
abandoned but was retained primarily for agriculture because of its
agreement with the seasons. Thus, the ancient Egyptians operated with three
calendars, each for a different purpose.
The only unit of time that was larger than a year was the reign of a king. The usual custom of dating by reign was: "year 1, 2, 3 . . . , etc., of King So-and-So," and with each new king the counting reverted back to year One. King lists recorded consecutive rulers and the total years of their respective reigns.
civil year was divided into three seasons, commonly translated: Inundation,
when the Nile overflowed the agricultural land; Going Forth, the time of
planting when the Nile returned to its bed; and Deficiency, the time of low
water and harvest.
months of the civil calendar were numbered according to their respective
seasons and were not listed by any particular name--e.g., third month of
Inundation--but for religious purposes the months had names. How early these
names were employed in the later lunar calendar is obscure.
days in the civil calendar were also indicated by number and listed
according to their respective months. Thus a full civil date would be: "Regnal
year 1, fourth month of Inundation, day 5, under the majesty of King
So-and-So." In the lunar calendar, however, each day had a specific name,
and from some of these names it can be seen that the four quarters or chief
phases of the Moon were recognized, although the Egyptians did not use these
quarters to divide the month into smaller segments, such as weeks. Unlike
most people who used a lunar calendar, the Egyptians began their day with
sunrise instead of sunset because they began their month, and consequently
their day, by the disappearance of the old Moon just before dawn.
As was customary in early civilizations, the hours were unequal, daylight being divided into 12 parts, and the night likewise; the duration of these parts varied with the seasons. Both water clocks and sundials were constructed with notations to indicate the hours for the different months and seasons of the year. The standard hour of constant length was never employed in ancient Egypt.