Ancient Egyptian Day

Not to be confused with Egyptian days.

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The Ancient Egyptian Day began at sunrise

A Day in Ancient Egypt corresponded to 24 ancient Egyptian hours, divided into "twelve day hours" and "twelve night hours." The twelve day hours typically began with sunrise and lasted until sunset, followed by the twelve night hours. The hours were unequal with their length varying by season, and being equal at the Equinox. The visible Sun thus marked the light day. Therefore, in the Egyptian Calendar, the date changed not at midnight, as in the Gregorian Calendar and Julian Calendar, but with sunrise.

The first day of the month in the Ancient Egyptian Lunar Calendar began right at the instant the waxing crescent moon became invisible in the dawn before sunrise. Since the last night hours belonged to the old day, the invisibility of the moon was a reliable signal immediately before the rising sun. At new moon, sighting a crescent moon is generally not possible, as the moonrise occurs almost simultaneously with the sun without crescent formation, and the new light moon cannot be seen with the naked eye.

The ancient Egyptian day always dated over the period of two Julian or Gregorian days. Heliacal risings of stars always belonged to the old day, which is why they are to be backdated by one day in the Julian or Gregorian calendar. For example, if Sirius as the signal for the Nile Flood had its heliacal rising on June 20, this event in the ancient Egyptian calendar still counted for June 19. According to this definition, the arrangements of the Diagonal Star Clocks and the entries in the Book of Nut are made. There, all visible Decans are divided into the phases of heliacal rising, acronychal culmination, and acronychal setting and assigned to an ancient Egyptian day: "One Decan dies (acronychal setting) and another lives (heliacal rising) at the beginning of a Decan."

Definition of the Ancient Egyptian Day

The sun god Ra in his solar barque
(Tomb of Seti I)

The Egyptian calendar was divided into 36 weeks, each encompassing ten days. Every week began with the Decan-Day, based on the heliacal rising of the respective Decan Star. The last five days of the year were known by the Egyptians as Heriu-renpet (Epagomenal days).

In Egyptology, there have been controversial discussions in the past about the start time of an ancient Egyptian day. Due to unclear statements in sources attributed to Egyptian mythology, some Egyptologists included the morning and evening twilight in the 12 daylight hours. However, in texts of Egyptian astronomy related to the ancient Egyptian calendar, the 12 daylight hours are defined from sunrise to sunset.

The definitions made by Egyptologists in older literature sometimes contradict each other. Therefore, it is possible that the literature of those Egyptologists who define the start of the day from twilight is used, while at the same time, they set the start of the day from sunrise elsewhere. For example, Richard Anthony Parker and Otto E. Neugebauer state:

The first hour of the night begins with the darkness after sunset and no star is needed to indicate it (the First night hour)... The heliacal rising was crucial for the selection of the Dekan stars, as the Dekan marks the Twelfth night hour.

The significantly improved astronomical calculation possibilities in recent times and the emergence of new textual sources led to reevaluations of historical texts and corrections of erroneous statements in existing older literature in Egyptology. Egyptologists and astronomers uniformly confirm that, contrary to the “invisible 70 days of Sirius” mentioned in ancient Egyptian sources, 74 days can be astronomically proven at the observation site Memphis, Egypt during the Early Dynastic Period. This finding also contradicts the equating of the 1st and 12th daylight hours with twilight phases, which furthermore could not be captured by the ancient Egyptian sundial due to the lack of shadow. Thus, the 12 daylight hours marked on the ancient Egyptian sundial referred to the bright day.

Mythological Definition

Ceiling depiction (Tomb of Seti I.)

In ancient Egyptian mythology, the division of the twilight hours holds a special significance, as documented in the Hourly calendar of Ramses II. The Nut-book representations in the tomb of Seti I (Tomb of Seti I) in the Valley of the Kings describe this unique situation: "The locations of the first two night hours are the hands and lips of the sky goddess Nut". The entry of Ra into the Duat coincides with the "swallowing of Ra". The transformation of "Ra in Heliopolis as the sun of the day" into the evening form of Atum vividly represents the special situation of "Re's in-between time".

Therefore, in Egyptian mythology, the first two night hours could still be counted as part of the day, as the "hours of the night" originally began with the "swallowing of Ra". Similarly, this concept applied to the last two hours of the night, during which Ra, in the "process of birth", left the Duat but had not yet reached the horizon and appeared as dawn in the form of the deity Khepri.

Calendrical Definition

Day

Diagonal Star Clock from the Middle Kingdom of Egypt

In calendar computation, the principle of solar visibility was consistently applied. The term "day" is associated with the appearance of the sun god Ra. Thus, the Egyptians called "every day" also "every sun". In the "Tale of the Two Brothers," the beginning of the day is described as "When the earth became light for the next day". The "becoming light" still referred to the dawn, which at the same time marked the twelfth hour of the night. Accordingly, the time after sunset was considered "second half of the day, the darkness that follows Ra."

Christian Leitz refers to the statement by Richard-Anthony Parker and Otto Neugebauer "The first hour of the day begins with the dawn" as "not acceptable", as it contradicts ancient Egyptian sources. There, for example in the Book of Nut and in the diagonal star clocks, the heliacal rise is consistently timed for the 12th night hour. Moreover, the acronychal settings and acronychal culminations during the evening twilight are considered as entry into the Duat, which occurs in the 1st night hour.

On the Naos of the Decades of Nektanebos I., the effectiveness of the decans begins with the culmination at the end of the 12th night hour. Alexandra von Lieven refers in this context to the function of the dawn, which is to be regarded as the "birth phase of the sun god," with Ra still being below the horizon. Similarly, the decan stars are titled "those born in the 12th night hour" during the dawn and located above the "exit gates of the Duat."

The sun god Ra immediately after leaving the underworld gates during "the hour that satisfies"

In ancient Egyptian mythology, the beginning of the first hour of the day is also described as "the moment when the sun god Ra leaves the area of the Mesqet and the Duat". The original version of the Book of Nut states further:

Thus arises [the command] that he (Re) distances himself to the sky, in the "hour that satisfies". Thus his form becomes strong and large. At night, the (decan stars as) Bas appear in the sky. The decan stars follow Re in his rising in the "hour that satisfies". During the day they are not visible to humans.

— Nutbuch, Seti I script:

The times of day in Ancient Egypt were represented by the hour goddesses. Richard-Anthony Parker and Otto Neugebauer "postulated" that "the hour that satisfies" is otherwise not verifiable in ancient Egyptian texts. Since the "hour that satisfies" belongs to the day, it is indeed unknown in the Book of the Night, but documented in the Book of the Day: "The majesty of this god appears in the hour 'That reveals the beauty of Ra'. This is the hour that satisfies." In addition, this hour is mentioned two more times regarding the sun's course in the Book of Travelling Through Eternity. The Papyrus Carlsberg 1, originating from the Greco-Roman period in Egypt, is a copy of the original versions of the Book of Nut from the New Kingdom. The Papyrus Carlsberg 1 contains numerous new theological interpretations.

Re commands his removal from the humans in the Duat, in the ninth hour of the night, that is, in the "hour that satisfies". The decan stars make their journey when pulling in the sky. Their risings are invisible to the human eye. His (Re's) gaze upon the earth at rising are his rays.

— Nutbuch, Papyrus Carlsberg 1

Night

Twilight as the 1st Night Hour

The night began with twilight immediately after sunset in the Twelfth Hour of the Day and ended with sunrise. The end of the twelfth night hour also marked the end of the Egyptian day. The arrangement of the decans on the diagonal star clocks contradicts the hypothesis that the 1st night hour only begins after twilight. A decan was fundamentally the “signal” and “name giver” for the duration of 10 days each.

The stars associated with a decan had significantly less brightness than Sirius, which is why under normal conditions those stars were only visible about 50 to 60 minutes after sunset and immediately thereafter either culminated or set acronychically. The corresponding statements about the “death of a decan” at its acronychical setting always referred to the 1st night hour. Therefore, the decan stars representing the decan always indicated the end of the 1st night hour, shortly followed by the beginning of the 2nd night hour.

Nocturnal Sun Course
(Depiction in KV11)

What is between the star that makes the 1st hour (of the night) (Culmination), that is, the evening star, to the one that circles the Duat (acronychical setting), these are 9 stars…The majesty of this god (Re) enters (into the Duat) with respect to the 1st hour (of the decan stars) in darkness…The majesty of this god (Re) rests…in the Duat in the 2nd hour of the night.

— Nutbuch, Decan chapter

In the “Book of the Night,” the barque night journey of Ra also begins in the 2nd hour of the night, while Seth stands at the “shore of the lake,” over which the dying decan (1st night hour) still floats and slightly touches him. The sun god Ra can only board his barque if he has unscathed passed the “Gate of the All-Devourer (Seth)” at the beginning of the 2nd night hour. A night hour corresponded to 50 minutes on the longest day of the year, and 70 minutes on the shortest day. From the time of sunset to the end of the astronomical twilight in Egypt, it takes an average of about 90 minutes, so the phase of total darkness always fell into the 2nd night hour.

Ra in the Sun Barque during the Night Journey

In the “Tale of Two Brothers,” after sunset, the just-passed day is referred to as “Yesterday” and as “Time that does not belong to Ra.” Thus, the nights of ancient Egyptian festivals always fell on the previous day, even if the festival's start was in the time immediately after sunrise. Also, the Ancient Egyptian New Year's Festival began “on the night of the fifth day of the season Heriu-renpet.” With the first rays of the sun of the first Achet I, the new year arrived shortly thereafter, while the “birth of Ra” had begun in the old year and was completed at the time of sunrise. Sopdet could also act as a “midwife” during dawn as a manifestation of Isis or Hathor.

Day Lengths

The length of a day or night hour varied on average depending on the season typically between 1 hour 9 minute and 51 min. The average day and night lengths had in conversion a fluctuation range of 10 h 21 min (December 21/22) to 13 h 44 min (June 21/22).

The mentioned times apply to the observation location Memphis, Egypt. The values change depending on the latitude, with the twilight phases showing increasing lengths towards the north and decreasing lengths towards the south.

Duration of Twilight, Day and Night in Memphis
State of Light	March 20/21	June 21/22	Sep. 22/23	Dec. 21/22
Astronomical Twilight	04:39 AM	03:22 AM	04:24 AM	05:21 AM
Nautical Twilight	05:07 AM	03:55 AM	04:52 AM	05:51 AM
Civil Twilight	05:35 AM	04:29 AM	05:20 AM	06:21 AM
Sunrise	06:00 AM	04:55 AM	05:44 AM	06:47 AM
Sunset	06:03 PM	06:56 PM	05:47 PM	04:56 PM
Civil Twilight	06:28 PM	07:22 PM	06:14 PM	05:25 PM
Nautical Twilight	06:58 PM	07:55 PM	06:47 PM	05:58 PM
Astronomical Twilight	07:29 PM	08:30 PM	07:20 PM	06:31 PM
Duration of Night (total darkness)	07:29 PM – 04:38 AM	08:36 PM – 03:21 AM	07:20 PM – 04:23 AM	06:31 PM – 05:20 AM
Duration of Day (daylight)	06:00 AM – 06:03 PM	04:55 AM – 06:56 PM	05:44 AM – 05:47 PM	06:47 AM – 04:56 PM
Duration of Night Hour	00:59:45	00:49:55	00:59:45	01:09:15
Duration of Day Hour	01:00:15	01:10:05	01:00:15	00:50:45

Bibliography

• Rolf Krauß: Sothis- und Monddaten: Studien zur astronomischen und technischen Chronologie Altägyptens. Gerstenberg, Hildesheim 1985, ISBN 3-8067-8086-X Search this book on ..
• Christian Leitz: Studien zur ägyptischen Astronomie. Harrassowitz, Wiesbaden 1991, ISBN 3-447-03157-3.
• Christian Leitz: Altägyptische Sternuhren. Peeters, Leuven 1995, ISBN 90-6831-669-9.
• Ulrich Luft: Der Tagesbeginn in Ägypten: Der Tag begann bei Sonnenaufgang. In: Altorientalische Forschungen. (AoF) Nr. 14. Akademie, Münster 1987, S. 3–11.
• Jean Meeus: Astronomische Algorithmen – Anwendungen für Ephemeris Tool 4, 5. 2. Auflage. Barth, Leipzig/ Berlin/ Heidelberg 2000, ISBN 3-335-00400-0.
• Jean Meeus: Astronomical Tables of the Sun, Moon and Planets. 2. Auflage. Willmann-Bell, Richmond 1995, ISBN 0-943396-02-6
• Richard Anthony Parker, Otto E. Neugebauer: Egyptian Astronomical Texts. (EAT), Band I. Brown University Press, Rhode Island 1969.
• Siegfried Schott: Altägyptische Festdaten. Verlag der Akademie der Wissenschaften und der Literatur, Mainz/ Wiesbaden 1950.
• Alexandra von Lieven: Grundriss des Laufes der Sterne – Das sogenannte Nutbuch. The Carsten Niebuhr Institute of Ancient Eastern Studies (u. a.), Kopenhagen 2007, ISBN 978-87-635-0406-5.
• Alexandra von Lieven: Der Himmel über Esna – Eine Fallstudie zur religiösen Astronomie in Ägypten am Beispiel der kosmologischen Decken- und Architravinschriften im Tempel von Esna. Harrassowitz, Wiesbaden 2000, ISBN 3-447-04324-5.

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