The
Nile, the Moon and Sirius:The Ancient Egyptian Calendar
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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