Ancient Egyptian Calendar

The Ancient Egyptian Calendar was similar to the Roman and Greek Calendar in that it followed the lunar cycle of 30 days, but then differed markedly because it followed the Annual Rise of the Nile.
This meant it had three seasons instead of four, and a month was three weeks long, because each week had ten days.

The Ancient Egyptian Calendar followed the three cycles of the Nile consisting of three cycles of 4 months with each month having 30 days.
Each month had 3 weeks, each consisting of 10 days called the Decan.
This gave a year of 360 days, with a 5 day New Year festival added to make up the 365 days in the year.

Akhet:
- The Inundation season.
- The Annual Rise of the Nile occurred from mid July to mid November.
- The first rise of the Nile was recorded by the Nilometer at Elephantine Island on the border with Nubia.
Peret:
- The Season of Emergence (Winter).
- The Retreat of the Nile, occurred from early January to early May. It left the rich black silt deposit, and planting the crops could begin,
Shemu:
- The Season of the Harvest.
- This occurred in early May to early September.
The Five Epagnomal days:
- - These extra days brought the number of days in the year from 360 to 365.

The Sundial showed the passage of the Sun by the moving shadow from a Gnomon pointing towards the Pole Star.
The shadow moved across markings that accurately recorded the hour and minutes of the day.
Each Day was divided into 24 hours of equal length. 12 Daytime hours and 12 Nightime hours.

By 2,100 BCE, the Ancient Egyptians had created a Sidereal Star Clock, as a method of telling the time at night.
This was based on the Heliacal Rising of 36 groups of star constellations, known as the Decan Stars, one Decan group for every 10 degrees in the 360 degrees of the Zodiac.
Each ten degrees represented one Decanal ‘hour’ in the Sidereal Star Clock.
As the Earth rotates through ten degrees, one of the 36 Decans will have a Heliacal Rising in a fixed sequence, and the time in hours and minutes can be calculated.

Every ten days there is a Heliacal Rising of a new Decan Star Constellation.
The Ancient Egyptian Year started with the Heliacal Rising of Sirius, (which then occurred in Early July) which was followed by a new Decan Star starting every ten days.
Three Decan Constellations were grouped into each of the twelve divisions of the Zodiac.
Each Sign of the Zodiac was divided into 3 groups of ten day periods.
The Ancient Egyptian Year consisted of 3 Periods, each consisting of 4 months of 30 days.
This Calendar was based on the ten day divisions and is described in the Book of Nut.

Elephantine Island