The calendars (plural) used by the ancient Egyptians are the subject of a great deal of scholarship. A full presentation of the subject is beyond the scope of these notes. A classic on the subject which is freely available for personal use is Richard Parker’s The Calendars of Ancient Egypt, Studies in Ancient Oriental Civilization, No. 26, Chicago: University of Chicago Press, available from the publishers in PDF form at this link: https://isac.uchicago.edu/sites/default/files/uploads/shared/docs/saoc26.pdf. A more recent work on the subject, but not freely available, is Civil Calendar and Lunar Calendar in Ancient Egypt by Leo Depuydt.
The purpose of this page is to provide a few brief notes about what our online Egyptian Calendar does and does not provide for the user. For readers less familiar with how the Egyptian calendar systems worked, we have provided a “Background” section below. A reader familiar with the calendars may simply go on to the next section and read about our webapp.
Purpose and Limitations of our Webapp
The owner of this website identifies as Kemetic (that is, devoted to the Egyptian gods) and wanted an “Egyptian-like” calendar for his own use. There are various problems with this, and modern Kemetic groups and individuals have chosen solutions for themselves. The main issues are (1) when is wp rnpt (since the heliacal rising of Sirius happens on different days around the world); (2) does the calendar incorporate a leap year mechanism; (3) lunar or civil.
The solutions I have chosen for myself, and which this webapp assumes, are as follows: (1) allow the devotee to choose a date of wp rnpt based on the rising of Sirius where they live or a key location in Egypt; (2) yes; (3) civil. The details are:
- wp rnpt. The webapp lets you pick which city you’re calculating from. On the request of personal friends, several different American cities are in the list. Additionally, several places in Egypt (Heliopolis, Karnak, Tjebu) are there for someone who wants something more “traditional”. The webapp does not do astronomical calculations itself; rather, I have stored the pre-calculated dates of the heliacal rising for every city for the years 1950 to 2099 of the Christian era. I obtained these from Dominic Ford’s excellent website in-the-sky.org.
- Leap mechanism. The annual heliacal rising of Sirius is always either 365 days or 366 days after the previous one. For each city and chosen date, we just look at the most recent previous rising of Sirius and calculate from there. If it happens that you have chosen a date that, for the given city, is exactly 365 days since the last rising without having a rising that morning, then the webapp will show that you are looking at a leap day. We are relying on the pre-calculated dates of Sirius rising; we do not calculate one leap year simply based on the previous one.
- Lunar vs. civil. Evidence has shown that many Egyptian festivals transferred, over the course of dynastic history, from the lunar to the civil calendar. Since my “favorite” part of Egyptian history is the late New Kingdom and early Third Intermediate Period, I have chosen to go with the civil calendar.
Background
The start of the calendar
The beginning of the Egyptian year originally derived from an annual astronomical event known as wp rnpt or Wep Renpet, Egyptian for “Opening of the Year.” This was the heliacal rising of the star Sirius. For a little over two months of summer, Sirius is invisible in Egypt. The heliacal rising is the moment when, for the first time after its disappearance, Sirius rises just before dawn and can be seen, sometimes for only a couple of minutes, before the rising Sun’s light obscures it again.
Lunar and Civil Calendars
The lunar calendar consisted of twelve months (in most years) defined by the phases of the moon for a total of about 354 days. The original starting point for counting the months may have been the new moon immediately following wp rnpt. However, 354 days is too short to stay in sync with wp rnpt and with the seasons, so every few years an additional (intercalary) month was added after the twelfth month but before the first month of the new year. This allowed the lunar calendar to “catch up” with Sirius and the seasons.
Later the 365-day civil calendar was adopted. This consisted of three seasons: Akhet (ꜣḫt) “inundation”, Peret (prt) “emergence”, and Shemu (šmw). Each season in turn consisted of four 30-day months, for a total of 12 months and 360 days. Additionally, after the last month of šmw, there were five epagomenal, or intercalary, days, believed to be the birthdays of the children of the deities Geb and Nut.
Relationship between Lunar and Civil Calendars
The general view of the competing calendars is that the lunar calendar was used for determining religious festivals and temple rites, while the civil calendar was used for secular, governmental matters, things like tax collection or appointment of officials.
Parker proposes that the civil calendar led to a change in deciding when to add a thirteenth month to the lunar calendar. Before the civil calendar, it was purely connected with the rising of Sirius, but after the civil calendar had been in use for some number of years (perhaps centuries), it would have also fallen out of sync with Sirius, owing to its lack of a leap year. Rather than fixing the civil calendar, Parker says, a “later” lunar calendar came into being, in which the extra month was added so the lunar calendar would keep up with the civil calendar, and both calendars would then neglect the rising of Sirius.
Writing the Date
The lunar calendar had names for all thirteen of its months. The civil calendar did not, at least at first; months simply were given a number for their position within the season, so they were called “I ꜣḫt“, “II ꜣḫt“, “III ꜣḫt“, “IV ꜣḫt“, “I prt“, and so on through “IV šmw.” The full date for a given day would be written after that. So the 12th day of the fourth month of Inundation would be written as “IV ꜣḫt 12.” (Egyptologists have customarily used Arabic numerals for the day and a Roman numeral for the position of the month within the season.) Eventually the civil calendar months were given individual names as well, seemingly derived from the lunar calendar names and important festivals.
Leap Years and Calendar Sync
The lack of any leap year corrections in the civil calendar meant that it was soon out of sync from the rising of Sirius, but the Egyptians seem to have made no attempt to correct this until the Ptolemaic period, when Ptolemy III proposed adding a sixth epagomenal day every four years. This was not accepted by the priests and populace, and it was not until Augustus imposed it over two centuries later that this was done.
The Coptic Calendar
That final system (which is tied to the Julian, rather than the Gregorian, calendar) is still used today for the calendar of Coptic Orthodox Christians. Despite their religion, Coptic Christians have kept the names of the months, some of which derive from (or simply are) the names of Egyptian deities such as Thoth and Hathor. The present date on the Coptic calendar is shown in our webapp; its date does not depend upon the location chosen. The Coptic year is the “Year of the Martyrs” (anno martyrum), which began with the reign of Diocletian, and is 283-284 years (depending on time of year) lower than the Gregorian year number.