Egyptian calendar

An ancient Egyptian civil calendar with twelve 30-day months and five additional days at year’s end, totaling 365 days. It did not include a leap day, so its dates drifted against the seasons.

Egyptian civil year: The 365-day year used in ancient Egypt, divided into twelve 30-day months and five additional days. This calendar’s basic structure was a fixed civil year without a leap day.
Nile flood: The annual rise of the Nile that deposited water and fertile silt across its floodplain. Its predictable cycle shaped the calendar’s season of inundation.
Egyptian chronology: The system for ordering events and reigns in ancient Egyptian history. Calendar dates help historians place records within regnal years.
Canopus Decree: A Ptolemaic decree issued in 238 BCE that proposed adding a leap day every four years. It attempted to prevent the civil calendar from drifting through the seasons.
Egyptian months: The twelve 30-day divisions of the Egyptian civil year, grouped into three seasons. Each month had the same length, regardless of lunar phases.
Egyptian lunar calendar: A lunar system used in ancient Egypt to organize months by the phases of the Moon. It offered a month-based alternative to the fixed civil calendar.
Egyptian civil administration: The officials and institutions that managed taxation, labor, land, and resources in ancient Egypt. A standardized year supported recurring administrative schedules.
Alexandrian calendar: A calendar reform that added a leap day every fourth year to the Egyptian civil calendar. It retained the Egyptian month structure while correcting the year’s drift.
epagomenal days: Five days added after the twelve Egyptian months to complete a 365-day year. They supplied the five days beyond the calendar’s twelve 30-day months.
heliacal rising: The first visible dawn appearance of a star after a period hidden near the Sun. The heliacal rising of Sirius supplied a seasonal marker before civil dates drifted.

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