365-day civil calendar
Calendario civil de 365 días
- Date
- c. 2800 BCE · confidence medium
- Place
- Memphis and Heliopolis, Egypt
- Credited to
- Egyptian priest-astronomers
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What it is
Year of twelve thirty-day months plus five epagomenal days, originally anchored to the heliacal rising of Sirius and the Nile flood. It is the first solar administrative calendar, not lunar, and the direct ancestor of the Julian and Gregorian calendars.
The date of its establishment is debated, between c. 2800 and 2400 BCE; the lack of a leap year made the calendar drift by 1 day every 4 years (the 1,460-year Sothic cycle).
What it led to
- Annual planning of sowing, taxes and corvée without depending on lunar observation
- Uniform dating of documents by regnal year, the basis of historical chronology
- Rome's Julian reform, drawn from the Egyptian model via Alexandria
- The concept of an abstract, regular civil time independent of natural cycles
Built on
- Egyptian hieroglyphsc. 3200 BCE
- Neolithic lunar calendar
- Observation of Sirius (Sopdet)
Made possible
- Great Pyramid: large-scale ashlar engineeringc. 2560 BCE
- Sundial / shadow clockc. 1500 BCE
- Julian calendar45 BCE
- Egyptian sundial
- Chronology of reigns