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The Nile, the Moon and Sirius:
The Ancient Egyptian Calendar
By Richard
Weininger
The star-sprinkled Egyptian night sky that not
only stuns visitors to Egypt was also
studied intensely by special temple priests who soon discovered
that the appearance of a star they named sepdet (which we know as
Sirius) was associated with the beginning of the Nile flood . This
was the start of the world's first calendar, invented over 5000
years ago.
To develop a calendar, you need a regular event
that is predictable. And what was more
regular and important to the ancient Egyptians than the rise
and fall of the River Nile?
The waters started rising around the end of
June, and the flood period (achet) lasted until October, covering
the land with rich black mud and preparing
it for the sowing and growing period (peret). The harvest time (schemu)
started at the end of February and ended with the new Nile flood
This predictable, ongoing cycle defined the
agricultural year.
But there was a problem! The flood came within a
range of 80 days with variable intensities
.... all in all, not very accurate timing.
Sirius, or Sothis as it was called by the
ancient Egyptians, the star who's heliacal
rising was in early July 3000 years ago, but due to the wobble of
the earth on its axis is now a few weeks later,
turned out to be a very reliable predictor
of the recurring flood and defined the exact length of the trip
of the earth around the sun . (Sirius also revealed the entrance
to the tomb of Akhenaton in the novel The
Watch Gods by Barbara Wood. )
From their mythology, the Egyptians saw a
connection between Sepdet's appearance and
the beginning of the Nile flood. They believed the Nile flood was
caused by the tears that Isis ( the Great Mother of All Gods and
Nature ) shed, after her husband Osiris was murdered by his
brother Seth. Sepdet was the cosmic appearance of Isis.
The first new moon following the reappearance of
Sirius after it disappeared under the
horizon for 70 days was established as the first day of the New
Year ( Egypt: wepet senet) and of the achet (flood)
period--even if the Nile had not yet started
to rise.
The priests also observed there were four moon
periods that fit into each of the three
seasons --or rather didn't quite fit! The lunar month has 29 ½
days, resulting in "short" or
"long" years of 12 or 13 new moons.
It didn't really matter because the appearance
of Sirius and the next New Year put the
calendar back to baseline.
But, as in our times, this calendar was not
accurate enough for the central administration;
taxes and other things have to be paid on time. So in the Old
Kingdom, a standard calendar with 12 months of 30 days each was
introduced . Each month was divided into decades of
10 days.
Because this public calendar with 360 days was
too short to coordinate with the
agricultural and lunar calendar, five extra days called the heriu
renpet were added at the end of the year and
celebrated with religious festivities.
With this last calendar reform before Roman
times, the ancient Egyptians missed the true
length of the solar year by only ¼ day. But the missing days
added up and the gap between the lunar calendar and the public
calendar increased by one day every four years . So, in 1460 years
the calendar slipped through a whole year, meaning that in
between, according to one calendar, it could be harvest time,
although in reality the floodwaters were just receding!
This little "big problem" wasn't
solved until Augustus introduced the ‘leap year’
in Egypt around 30 B.C.
Winter and spring are the best time to watch
Sirius. In February, Sirius stands low in
the southeast and is the brightest star in the sky ----- go and
look ------ and imagine the Egyptian priests doing
the same 5000 years ago.
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