Egyptian Hour System

egyptian: wnwt

Definition

The Egyptian hour system splits the day-and-night cycle into 12 hours of daylight (hrw) and 12 hours of night (grh) — a 24-hour day. The basic unit is the wnwt, the hour. These hours are seasonal, not equal: their length shifts across the civil year, worked out month by month on a fixed scheme rather than measured against any true equal-hour standard. The night hours were first set by watching the stars, using decanal star-clocks and transit-clocks, before water-clocks and shadow-clocks were added to that stellar timing.

In Tradition

Egyptians fixed the hours of the night by the rising or meridian-crossing of particular stars. The instruments run from the Middle Kingdom diagonal-star (decanal) clocks of the Meshet coffin lid, through the Ramesside transit-based star clock (24 half-month tables, four surviving copies in the tombs of Ramesses VI, VII, and IX), to the Senenmut ceiling tradition. Clagett, Neugebauer, and Parker treat these as the canonical timekeeping instruments; the daylight hours are recorded in Cairo Papyrus 86637.

In Practice

A priest or astronomer read the hour of the night either by watching which decan was rising — the Middle Kingdom diagonal clocks — or by watching a star cross a 7-line meridian grid, the method of the Ramesside Star Clock. In the transit method, two observers sat on the temple roof facing each other along the meridian, with sighting sticks and plumb lines; they named the hour-star as it crossed through marked positions on a target figure — left shoulder, right shoulder, left eye, right eye, and so on. Each half-month of the civil year (the 1st to the 15th, the 16th to the month's end) had its own table of 13 transit positions: a "Beginning of Night" entry plus 12 "Hour-Ends." The daylight hours in Cairo Papyrus 86637, by contrast, use fixed month-by-month length values rather than anything measured by instrument.

Historical Origin

The 12-hour night is attested from the Old Kingdom onward. Middle Kingdom diagonal-star clocks survive on coffin lids from Asyut (Document III.11 in Clagett, Ancient Egyptian Science Vol II). The Ramesside Star Clock (Document III.14) dates to the 20th Dynasty of the New Kingdom. The daylight-length tables of Cairo Papyrus 86637 (Document III.7) date to c. 1400-1280 BCE, and the Tanis stone plaque (Document III.8) dates to Necho II of Dynasty 26.

Definition

In Tradition

In Practice

Historical Origin

Further Reading