Dating back to the dawn of civilization, the ancient Egyptian calendar stands as one of humanity’s earliest attempts to organize time. Originating at the beginning of the third millennium BC, this remarkable system represents the first known solar calendar in history, offering invaluable insights into the astronomical knowledge and cultural practices of ancient Egypt.

In Egypt, various calendars – the lunar, the solar (civil), and possibly a third secondary lunar calendar – were used to accurately calculate ephemeris.

The Egyptian astronomical priests discovered that lunar calendars were not practical to predict the beginning of the Nile floods, calculate the seasons or count long periods, and comparing them with a measurement referring to the apparent movement of the Sun and the stars, they preferred to use the solar calendar for civil uses, for the first time in history.

The Egyptians may have used a lunar calendar before, but when they discovered the discrepancy between the lunar calendar and the regular passage of the seasons, they probably switched to a seasonal calendar, basing their regular onset on each annual Nile flood.

The first flood according to The Calendar was observed in the first capital of Egypt, Memphis, at the same time as the heliacal rising of the star Sopdet ( Sirius ). The Egyptian year was divided into the three seasons of an agricultural nature:

• Flood (late summer and fall)
• Sowing (winter and early spring)
• Harvesting (late spring and early summer)