The Egyptian Calendar

Introduction and History of the Calendar

About 5000 years ago, the Egyptian kingdom had established along the river Nile. It existed for nearly 3000 years with some interruptions. Circumstances were favourable for the development of the Egyptian civilisation. Every year the river Nile brought fertile mud onto the fields ensuring rich harvests. Quite early Egyptian astronomers discovered the fact, that the flood of the Nile and the first visibility of the star Sirius on the morning sky, called heliacal rising, fell close together. It seems likely that the beginning of the Egyptian calendar year corresponded to a heliacal rising at the time the calendar was established. But, with the calendar year having invariably 365 days, the calendar shifted one day every four years with respect to the seasons. Thus, within 1460 Julian years (of 365.25 days each) 1461 Egyptian years elapsed. This period is called the Sothis Period (1). After a Sothis Period the calendar was in line with nature again.

There is no evidence of when the Egyptian calendar was established. The dates of three heliacal risings, during the reign of Thutmosis III., Amenophis I., and Sesostris III. (2), have come to us. The Roman historian Censorinus wrote that the heliacal rising fell on Egyptian New Year in 139 CE. If the heliacal rising of Sirius and the beginning of the year really corresponded at the time the calendar was introduced, one could reckon (3) the years 1322 BCE, 2782 BCE, or even 4242  BCE. Of course one cannot conclude the introduction of the Egyptian calendar has taken place in the 5th millenium BC from this reckoning alone.

It seems very unlikely that the shift of the calendar through the seasons was not recognized by ancient Egyptian astronomers. Nevertheless, no documents of any serious attempt to correct the calendar have been found yet that are older than the Canopus decree of king Ptolemaios III Euergetes (r 246 BCE-222 BCE). By this decree, in 238 BCE, Ptolemaios ordered an additional day to be added to every fourth year. But in practice the calendar remained unchanged. Only in 30 BCE, Caesar's successor Augustus reformed the Egyptian calendar.

The reform added a leap day to every fourth year, making the year of the Egyptian calendar as long as that of the Julian calendar. Thus, the beginning of the Egyptian year always fell on 29 August except in years preceding a Julian leap year, when the Egyptian year began on 30 August. The shift of one day was then corrected on 29 February the following Julian (leap) year. To distinguish this reformed Egyptian calendar from the original one, the former is sometimes called Alexandrinian calendar.

Unfortunately, the ancient Egyptians had no consecutive counting of the years. They instead wrote the number of the counting of the cattle that took place every other year. A year could be specified, for example, by writing ‘year of the 3rd counting [in king ...'s reign]’, or in a shorter manner, used later, ‘year of the 3rd time’. From the 11th dynasty (about 2100 BCE) the regnal year was written. The beginning of a regnal year was 1 Thot (see below) of the year in which the king came to power. Year one of a king who began his reign on the 3rd additional day would have 3 days only. Beginning with the 18th dynasty (about 1540 BCE) the regnal years were begun on the actual day on which the king came to power. This style was used until the 26th dynasty (about 660 BCE), when the former method came into use again.

Internal Structure

The year was divided into three seasons of four months each. Every month consisted of 30 days. At the end of the year, five additional days were added. Thus a year had 365 days. A date was given as ‘16th day of the 2nd month of the Inundation’, for example. Furthermore, the months were given names, too.

The seasons and months are compiled in the following table.


Interestingly the Egyptian months seem to have been disconnected from the moon's phases in a quite early stage of the development of the calendar. Thus, complicated mechanisms to keep the months in alignment to the moon were unnecessary which made possible an easy and clear internal structure.

The calendars of the Christians in Egypt and Ethiopia were derived from the Egyptian calendar and still have the same internal structure, see Coptic and Ethiopic Calendar.

Ptolemaic Egypt

After Egypt had become a part of Alexander the Great's empire it became a separate kingdom under the dynasty of Ptolemaios I Soter (r 323/305 BCE - 282 BCE), one of Alexander's commanders. After a short period of parallel usage of both the Egyptian and the Macedonian calendars, the Macedonian calendar was abandoned and just Macedonian month names applied to the months of the Egyptian calendar according to the following table.


At some time during the reign of Ptolemaios VIII Euergetes II (r 170/164 BCE - 163 BCE and 145/144 BCE - 116 BCE) the correlation was altered by shifting the Macedonian month names backwards by four months, see the table below.


Julian Reform

After Egypt had become Roman, the Egyptian calendar was adapted to the Julian by adding a sixth epagomenal day every four years. Since such an Egyptian leap year ends in every Julian year preceding a Julian leap year, the next Egyptian year begins on 30 August and the dates are shifted one day until the end of February of the Julian leap year. The following table shows the Julian dates of the first day of each month of the reformed Egyptian calendar. The dates in brackets are valid for a year following a leap year of the reformed Egytian calendar.

1 Thot29 (30) August
1 Paophi28 (29) September
1 Athyr28 (29) October
1 Choiak27 (28) November
1 Tybi27 (28) December
1 Mechir26 (27) January
1 Phamenoth25 (26) February
1 Pharmuthi27 March
1 Pachon26 April
1 Payni26 May
1 Epiphi25 June
1 Mesori25 July
1 epag.24 August




Sothis is the Greek name of Sirius. The Egyptian name was ‘spdt’. As the Egyptians wrote no vowels, Egyptologists are forced to use linguistic studies to ‘fill in’ the vowels. Today, the Egyptian ‘spdt’ is interpreted as ‘Sopdet’. The heliacal rising of Sirius seems to shift slowly with respect to the tropical year. Taking this shift into consideration, a Sothis period is slightly shorter than 1460 years, and using the term ‘Sothis period’ for the 1460 years it takes 1 Thoth to shift through the whole year then would not be correct. Nevertheless, as it is used in the latter sense quite often, I will do so, too.

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The names of kings, months, and seasons used here are mostly of Greek origin and do not necessarily correspond to the original Egyptian spellings. The three kings mentioned are called Dhutmose, Amenhotpe, and Senwosre nowadays.

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By subtracting 1460, which is the length of a Sothis Period, several times from 139.

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   © Holger Oertel 2000-2008; last change: 30 May 2009

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