The Ancient Egyptians relied on a lunar calendar until they migrated to a solar based calendar. While the exact genesis of the ancient Egyptians calendar remains unclear, Egyptologists estimate it was created some 5,000 years ago.
While their lunar calendar regulated their rituals and religious festivals, the ancient Egyptians employed a solar calendar in their daily lives. This solar calendar featured 365 days in their year. Each year was then divided into three seasons, the flood, growing and harvest seasons each of four months. These seasons reflected the annual rhythm of the Nile floods and their growing and harvesting cycle.
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Facts About The Ancient Egyptian Calendar
- The ancient Egyptian calendar remained in use through to the Middle Ages as its days and months were consistent
- Egyptians started their day at sunrise. In contrast, many nearby cultures began their day at sunset
- To tell time during the day ancient Egyptians used a mix of hourglasses, sundials and obelisks, while at night the stars were used. When water clocks were introduced the Egyptians could tell time more accurately
- The ancient Egyptian New Year was celebrated on July 19th when Sirius reappeared on their eastern horizon following a 70-day absence coinciding with the annual Nile floods
- A wandering year, the annus vagus not linked to Sirius’ appearance was inserted every four years to insert the extra day required to balance the solar calendar with the Egyptian calendar.
The New Kingdom Calendar
The ancient Egyptians original lunar calendar numbered the months according to where they fell during the season. In the New Kingdom, each month received an individual name. Civil dates were conventionally recorded as the number of the month that season, followed by the name of the season and the number of the day in that month and finally the year and the Pharaoh.
As a new Pharaoh ascended the throne the Egyptians restarted their year count. Astronomers during ancient times and throughout the Middle Ages employed the ancient Egyptian calendar as its regularity in both the number of days in each month and the year made their calculations considerably easier.
The Structure Of The Ancient Egyptian Calendar
The ancient Egyptian calendar featured:
- Weeks consisting of ten days
- Months had three weeks
- Each season was four months long
- A year was divided into three seasons plus five sacred days.
Akhet or flood or inundation was the first Egyptian season of the year. It included four months, Tekh, Menhet, Hwt-Hrw and Ka-Hr-Ka.
Proyet or emergence was the next season following Akhet. This was the primary growing season for Egyptian farmers. Its four months were Sf-Bdt, Redh Wer, Redh Neds and Renwet.
The final season in the Egyptian year was the harvest season known as Shomu or low water. It consisted of four months Hnsw, Hnt-Htj, Ipt-Hmt and Wep-Renpet.
A decades or decans represented each month of three ten-day periods. While each month had a precise name, they were usually known by their festival name. The final two days of each decade were holidays when the Egyptians weren’t obliged to work.
An ancient Egyptian solar calendar month lasted for 30 days. As this didn’t represent all the days in a single year, the ancient Egyptians included an extra month that slotted in at the end of the standard calendar year.
This additional month was only five days in duration, resulting in the Egyptian solar calendar losing one-quarter of a day each year compared to a physical solar year. Those five extra days were devoted to celebrating the birthdays of the gods.
The decans referred to in their calendar are star clusters used by the ancient Egyptian astronomers to note the time during the night. There were 36 decans of stars. Each decan comprised ten days, creating a 360-day long year.
Ptolemy III issued his Canopus Decree to provide for a sixth epagomenal day every fourth year to correct this gap. Both the Egyptian priesthood and its broader population resisted this decree. It was ultimately abandoned until 25 B.C and the advent of Augustus’ Coptic calendar.
While Egyptologists know the names of these decans, their current locations in the heavens and their connection to our contemporary constellations remain unclear.
The Ancient Egyptian Civil Calendar
This ancient Egyptian civil calendar was introduced at a later date. Egyptologists theorise it provided a more-precise calendar for accounting and administrative purposes. This civil calendar comprised 365 days structured into 12 months each having 30 days. An extra five epagomenal days were added at the end of the calendar year. These dual calendar systems remain in use throughout the Pharaonic period.
Julius Caesar revolutionized the Egyptian civil calendar around 46 BCE by including a leap-year day every four years. This revised model forms the basis of the Western calendar still in use right up to the present day.
The Ancient Egyptians divided their days into twelve-hour segments. These were numbered one to twelve. At night the hours were similarly divided into another twelve segments, numbered thirteen to twenty-four.
The daytime and nighttime hours were not of uniform duration. In the summer the hours of each day were longer than the nighttime hours. This reversed during the Egyptian winter.
To assist in telling the time during the day, the ancient Egyptians adopted a mix of hourglasses, sundials and obelisks, while at night they used the stars. With the introduction of water clocks, the Egyptians could tell time more accurately
Sirius’ Role In The Ancient Egyptian Calendar
The primary impetus for the ancient Egyptians in maintaining the accuracy of their solar calendar year compared to the physical solar year was to ensure the heliacal rising of Sirius occurred reliably. The heliacal rising took place when Sirius could be glimpsed briefly on the horizon prior to sunrise.
Sirius played a central role in Egyptian religion as well as regulating their annual cycle of Nile flooding. Aside from being the night sky’s brightest star, Sirius was captivated the ancient Egyptians for several reasons. Sirius was thought to power the sun. Sirius’ role was to keep the spiritual body alive, while the sun gave life to the physical body.
Ancient Egyptians closely linked Sirius to Isis the earth goddess forming one element in Egyptian mythology’s divine trinity. Egyptologists as astrophysicists have shown the Great Pyramid of Giza is aligned with Sirius. Sirius’ heliacal rising ushered in the start of the annual Nile floods.
After introducing astrology, the cyclical rise of the stellar decans was seen as portents for the onset of diseases and the optimal timing to apply their cures.
Reflecting On The Past
The sophistication of the ancient Egyptian culture can be seen in its adoption of advanced solar and civil calendar models. This innovation was initially stimulated by the need to track the annual inundation brought by the Nile floods, while a more accurate civil calendar proved effective for accounting and administrative purposes.