The Kemetyu Calender

At the outset the Kemetyu, like most of the peoples of antiquity, seem to have used a lunar calendar, notably to set the dates of religious festivals. But alongside that astronomical calendar they used another. A peasant people, their daily round was strongly marked by the rhythm of agricultural life: sowing, reaping, harvest home, preparation of the new seed. Now in Kemet the agricultural rhythm of the valley is set by the Nile, its changes determining the dates of the various operations. Hence there is nothing surprising in the fact that, parallel to a religious lunar calendar, the ancient inhabitants of the valley should also have used a natural calendar based on the periodic repetition of an event that was all-important for their existence – the flood of the Nile.

In that calendar the first season of the year, called ‘Akhet’ in Kemetyu, saw the beginning of the flood. The river’s waters rose little by little and covered the land dried up by the torrid summer. For about four months the fields would become saturated with water. In the next season the land gradually emerging from the flood waters became ready for sowing. This was the season of Peret, literally ‘coming out’, a term that no doubt alludes both to the ‘coming out’ of the land from the water and the ‘coming out’ of the vegetation. Once sowing was over the peasant awaited germination, then the ripening of the grain. In the third and final season the Kemetyu harvested and then stored the harvest. After that they had only to await the new flood and to prepare the fields for its arrival. This was the season of Shemou.

It is possible, and even highly probable, that for a very long time the Kemetyu were satisfied with this calendar. The year then began with the actual rise of the waters. The season of Akhet so initiated lasted to the actual retirement of the waters, which marked the commencement of the season of Peret. This in turn ended when the ripened grain was ready for the sickle, marking the beginning of the season of Shemou, which ended only with the new rise. It mattered little to the peasant that one season might be longer than another; what mattered to him was the organization of his work, which varied according to the three seasons.

At what moment and for what reasons did the Kemetyu link the flood of the Nile with the simultaneous appearance on the horizon of the sun and the star Sothis? This will surely be difficult to determine. No doubt that linking was the result both of repeated observations and of profound religious beliefs. The star Sothis (Sirius), in Kemetyu Sepedet, the Pointed One, was later to be identified with Isis, whose tears were thought to determine the flood of the Nile. Perhaps w e have here the reflection of a very ancient belief associating the appearance of the deified star with the rise of the waters. Whatever their reasons, by linking the beginning of the flood, and consequently the first day of the new year, with an astronomical phenomenon, the Kemetyu have provided us with a means of setting positive reference points for their long history.

At the latitude of Memphis the very gentle beginning of the flood took place about the middle of July. Observation over a few years appears to have sufficed to show the Kemetyu that the beginning of the flood recurred on average every 365 days. They thereupon divided their year of three empirical seasons into a year of twelve months of thirty days each. They then assigned four months to each of the seasons. By adding five additional days (in Kemetyu the ‘5 heryou renepet’, the five over – in addition to — the year), which the Greeks called the ‘epagomenes’, the scribes obtained a year of 365 days, which was by far the best of all those adopted in antiquity. However, although very good, that year was not perfect. In fact, the earth completes its revolution around the sun, not in 365 days, but in 365 and 1/4 days. Every four years the Kemetyu’ official year lagged one day behind the astronomical year, and it was only after 1460 years – what is called a Sothic period — that the three phenomena, sunrise, rise of Sothis and beginning of the flood occurred simultaneously on the first day of the official year.

This gradual lag between the two years had two important consequences: first, it enabled modern astronomers to determine when the Kemetyu adopted their calendar, that date necessarily having to coincide with the beginning of a Sothic period. The coincidence of the phenomena – beginning of the flood rise and heliacal rising of Sothis – occurred three times in the five millennia before our era: in —1325-1322, in —2785-2782 and in —4245-4242. It was long believed that it was between —4245 and —4242 that the Kemetyu adopted their calendar. It is n ow accepted that it was only at the beginning of the following Sothic period, that is, between —2785 and —2782.

The second consequence of the adoption by the Kemetyu of the fixed solar calendar was gradually to bring about a lag between the natural seasons determined by the very rhythm of the river itself and the official seasons used by the government which were based on a year of 365 days. This lag, at first barely perceptible, being one day every four years, increased little by little from one week to one month, and then to two months until the official calendar fell during the height of the natural season of Peret. This shift could not fail to strike the Kemetyu scribes, and we possess texts noting, very officially, the difference between the real heliacal rising of Sothis and the beginning of the official year.


The terms: Black Egypt, Pharaonic Egypt and Ancient Egypt or Egypt have all been replaced with the more appropriate term ‘Kemet’.

Whereas the terms: Black Egyptians, Pharaonic Egyptians and Ancient Egyptians or Egyptians  have all been replaced with the more appropriate term ‘Kemetyu’.

For a scholarly explanation on the above changes; see ‘The Egyptians as they saw themselves’.


Authors: R. El Nadoury with collaboration of Vercoutter. General History of Africa Vol.II. [Editor: G.Mokhtar] Ancient Civilisations of Africa. Chapter 5. Legacy of Pharaonic Kemet.

R. El Nadoury (Egypt); specialist in ancient history; author of numerous works and articles on the history of the Maghrib and of Egypt; Professor of Ancient History and Vice Chairman of the Faculty of Arts, University of Alexandria.

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  1. Kemet and Astronomy | African Progressive

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