Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of days or months.
A month is a unit of time, used with calendars, that is approximately as long as a natural phase cycle of the Moon; the words month and Moon are cognates. The traditional concept of months arose with the cycle of Moon phases; such lunar months ("lunations") are synodic months and last approximately 29.53 days, making for roughly 12.37 such months in one Earth year. From excavated tally sticks, researchers have deduced that people counted days in relation to the Moon's phases as early as the Paleolithic age. Synodic months, based on the Moon's orbital period with respect to the Earth–Sun line, are still the basis of many calendars today and are used to divide the year.
Sopdet is the ancient Egyptian name of the star Sirius and its personification as an Egyptian goddess. Known to the Greeks as Sothis, she was conflated with Isis as a goddess and Anubis as a god.
A solar calendar is a calendar whose dates indicate the season or almost equivalently the apparent position of the Sun relative to the stars. The Gregorian calendar, widely accepted as a standard in the world, is an example of a solar calendar. The main other types of calendar are lunar calendar and lunisolar calendar, whose months correspond to cycles of Moon phases. The months of the Gregorian calendar do not correspond to cycles of the Moon phase.
The Season of the Inundation or Flood was the first season of the lunar and civil Egyptian calendars. It fell after the intercalary month of Days over the Year and before the Season of the Emergence. In the Coptic and Egyptian calendars this season begins at the start of the month of Thout, continues through the months of Paopi and Hathor, before concluding at the end of Koiak.
The Season of the Emergence was the second season of the lunar and civil Egyptian calendars. It fell after the Season of the Inundation and before the Season of the Harvest. In the Coptic and Egyptian calendars this season begins at the start of the month of Tobi, continues through the months of Meshir and Paremhat, before concluding at the end of Parmouti.
The ancient Egyptian calendar – a civil calendar – was a solar calendar with a 365-day year. The year consisted of three seasons of 120 days each, plus an intercalary month of five epagomenal days treated as outside of the year proper. Each season was divided into four months of 30 days. These twelve months were initially numbered within each season but came to also be known by the names of their principal festivals. Each month was divided into three 10-day periods known as decans or decades. It has been suggested that during the Nineteenth Dynasty and the Twentieth Dynasty the last two days of each decan were usually treated as a kind of weekend for the royal craftsmen, with royal artisans free from work.
Thout, also known as Thoth and Tut, is the first month of the ancient Egyptian and Coptic calendars. It lies between 11 September and 10 October of the Gregorian calendar. The month of Thout is also the first month of the Season of Akhet (Inundation) in Ancient Egypt, when the Nile floods historically covered the land of Egypt; it has not done so since the construction of the High Dam at Aswan.
Paopi, also known as Phaophi and Babah, is the second month of the ancient Egyptian and Coptic calendars. It lasts between 11 October and 9 November of the Gregorian calendar, unless the previous Coptic year was a leap year. The month of Paopi is the second month of the Season of Akhet (Inundation) in Ancient Egypt, when the Nile floods inundated the land.
Hathor, also known as Athyr and Hatur, is the third month of the ancient Egyptian and Coptic calendars. It lies between November 10 and December 9 of the Gregorian calendar. The month of Hathor is also the third month of the season of Akhet (Inundation) in Ancient Egypt, when the Nile floods historically covered the land of Egypt; they have not done so since the construction of the High Dam at Aswan.
Koiak, also known as Choiak and Kiyahk, is the fourth month of the ancient Egyptian and Coptic calendars. It lasts between 10 December and 8 January of the Gregorian calendar, or between 11 December and 9 January of the Gregorian calendar in Coptic calendar years immediately following a Coptic calendar leap year. The month of Koiak is also the fourth month of the Season of Akhet (Inundation) in Ancient Egypt, when the Nile floods historically covered the land. They have not done so since the construction of the High Dam at Aswan.
Pashons, also known as Pachon and Bachans, is the ninth month of the ancient Egyptian and Coptic calendars. It lasts between May 9 and June 7 of the Gregorian calendar. The month of Pashons is also the first month of the Season of Shemu (Harvest) in Ancient Egypt, when the Egyptians harvest their crops throughout the land.
Paoni, also known as Payni and Ba'unah, is the tenth month of the ancient Egyptian and Coptic calendars. It lasts between June 8 and July 7 of the Gregorian calendar. Paoni is also the second month of the Season of Shemu (Harvest) in Ancient Egypt, where the Egyptians harvest their crops throughout the land.
Epip, also known as Epiphi and Abib, is the eleventh month of the ancient Egyptian and Coptic calendars. It lasts between July 8 and August 6 of the Gregorian calendar. The month of Epip is also the third month of the Season of Shemu (Harvest) in ancient Egypt, where the Egyptians harvest their crops throughout the land.
Mesori is the twelfth month of the ancient Egyptian and Coptic calendars. It is identical to Nahase in the Ethiopian calendar.
The intercalary month or epagomenal days of the ancient Egyptian, Coptic, and Ethiopian calendars are a period of five days in common years and six days in leap years in addition to those calendars' 12 standard months, sometimes reckoned as their thirteenth month. They originated as a periodic measure to ensure that the heliacal rising of Sirius would occur in the 12th month of the Egyptian lunar calendar but became a regular feature of the civil calendar and its descendants. Coptic and Ethiopian leap days occur in the year preceding Julian and Gregorian leap years.
The ancient Egyptian units of measurement are those used by the dynasties of ancient Egypt prior to its incorporation in the Roman Empire and general adoption of Roman, Greek, and Byzantine units of measurement. The units of length seem to have originally been anthropic, based on various parts of the human body, although these were standardized using cubit rods, strands of rope, and official measures maintained at some temples.
Sham Ennessim is an Egyptian national festival marking the beginning of spring, as it originates from the ancient Egyptian Shemu festival. It is celebrated by almost all Egyptians and is announced by the state as a public holiday. Sham Ennessim always falls on Easter Monday, which is the day after Easter, in accordance with the Coptic Orthodox Church.
The flooding of the Nile has been an important natural cycle in Nubia and Egypt since ancient times. It is celebrated by Egyptians as an annual holiday for two weeks starting August 15, known as Wafaa El-Nil. It is also celebrated in the Coptic Church by ceremonially throwing a martyr's relic into the river, hence the name, The Martyr's Finger. The flooding of the Nile was poetically described in myth as Isis's tears of sorrow for Osiris when killed by his brother Set.
The Opening of the Year Festival (wpy-rnp.t), also called the Beginning of the Year (tpy-rnp.t), Coming out of Sothis (pr.t-spd.t), the Birth of the King, and the Birth of Re (msw.t-Rꜥ), was an Egyptian festival celebrating the beginning of the year on the first of Thout. It was in correspondence with the Inundation of the Nile. The different titles were associated with different annual or semi-annual moments that fell on the same date, and possibly with different calendrical systems.
