Ptolemy Canon


  Greco-Egyptian Claudius Ptolemy lived in the city of Alexandria during the 2nd century AD. This astronomer worked at the Library of Alexandria and wrote a book called the Hé Magalé Syntaxis (The Splendid Order).

  After the Muslim invasion of 646, his work was known by the name of Almagest, and was the largest and most complete treatise on astronomy for 1,400 years, until Copernicus developed and published his theory. The Almagest records many eclipses and celestial phenomena, accurately dated in the year, day and time of the ancient Egyptian calendar of 365 days1, and it registers 19 eclipses that took place in the reign of various kings, covering a period of almost 900 years.

  The relation known as the Ptolemy Canon is actually an appendix of the Almagest; it is a list of the rulers of Babylon, Persia, Macedonia and Rome, numbered consecutively together with the length of their reigns. This dated sequence allows calculating the length of intervals between the astronomical observations mentioned in the Almagest.


  The canon starts at the beginning of the first year of the reign of the Babylonian king Nabonassar, which according to the exact intervals provided by the Almagest between that moment and the time of several eclipses, can be set at noon on February 27th, in the year 747 BC.

  In the first Babylonian period, every Egyptian year starts some 4 months earlier than the corresponding month of Nisan, as may be seen in the way in which the Egyptian years, fixed by the dates   of   the  eclipses   in   the   Almagest,    align   with   the   Babylonian   years,   fixed   by   the
tablet VAT 4956,  which sets the  37th year of the reign of Nebuchadnezzar  and similar tablet Strm Kambys 400 (also known as LBAT 1477, BM 33 066), which refers to the 7th year of the reign of Cambyses, scoring one of the recorded eclipses.

  The purpose of it was not to provide the complete record of all the kings of different kingdoms; it was only meant to assign a number of years of reign to each one of them; this is why it does not include any ruler who reigned less than a year and counts the year of ascension to the throne, regardless the date of the event, as a full year. The years of these reigns are not lunar or solar, but those of the ancient Egyptian calendar of 365 days, and while counting the time backwards, he recedes one more day every 4 years of the Julian calendar.


  The dating of the canon agrees with the astronomically fixed eclipse, of the 37th year of Nebuchadnezzar’s rule, but also with another of the preceding reign and with other three of the reign of Amel Marduk (the Evil Merodach of the Bible), the former only 26 years after the beginning of the canon.

  The ruling years of the kings listed by Ptolemy coincide with the Babylonian Chronicle and the Babylonian List of Kings, both of them on clay tablets. Therefore, confidence in that the canon provides reliable dates from the year 747 BC until it was written, may be considered well founded, for even if Ptolemy wrote his book several centuries later of the eclipses he recorded, we must consider that he certainly had the opportunity of consulting the copies of the original astronomical documents, stored in the library of Alexandria. For this reason, whenever the canon has been collated with the old documents of Babylon, Persia and Egypt, the dating in it has been ratified, demonstrating that the list compiled by Ptolemy, agrees with all the relevant archaeological documents.

  Ptolemy had at his disposal the documents which after several adversities, were still preserved in the library of Alexandria2, that despite what Plutarch says, was somewhat preserved until the Muslim invasion of 646.

  In the early 17th century, a copy of Ptolemy's canon was discovered among some Greek manuscripts and became rapidly the crucial instrument to date the pre-Christian period.

1) The calendars of Egypt and Babylon;


In ancient Egypt, one year was divided into three equal parts, each one of them with four months of 30 days. To those 360 days, were added 5 more days to celebrate the birth of the gods, which served to complete the year with 365 days; a year that was rectified every 4, without changing the number of days per month. Later, a sixth day was added to the calendar every 4 years. Each month was divided into 3 weeks of 10 days; the first period was from August 29th to December 26th and was Akhet, that of the flood and the overflow of the Nile; the second was Perets, the sowing time from, December 27th to April 25th; the third, Shemu, was harvest time, from April 26th to August 23rd; and at the end of the year, from August 24th to August 28th, were celebrated the 5 days of the gods.


The Babylonian calendar probably initiated like the Egyptian, according to the activities of each season, as the names of the 12 months that make it up, bring to mind. the months are: nisannu, ayaru, simanu, du'uzu, abut, ululu, tashritu, arahsamnu, kislimnu, tebetu, shabatu y addaru; which more or less mean: harvest; storing food; wheat of the gods; consume the malt; shear the sheep; collect the dates, etc. In any case, nisannu was the first month of the year and overlapped March and April, and addaru was the last one, overlapping February and March.    


2) The Museum and the Library of Alexandria, a wonder of the ancient world;


  Tradition says that Demetrius Falereo carried the personal library of Plato when he was expelled from Athens, and persuaded Ptolemy I to found the first public library and also the Museum (House of the Muses). 50 years later, the library already kept around 500,000 manuscripts and scrolls, and the Serapeion, another small public library, other 43,000.

  Some of the organizers of the library were Zenodotus of Ephesus, Callimaco of Cyrene, who created the file in the library, Aristophanes of Byzantium and Aristarchus of Samothrace, and there, were translated into Greek, like many other works, the biblical books of the Hebrew Scriptures, compiled in the version known as the LXX or 70.

  When in 47 BC, during the expedition of Julius Caesar a fire broke out because of the disorders in the city, the fire that began in the port, reached a warehouse that held 40,000 volumes, which were turned into ashes. Over time, the library suffered other setbacks, as that caused in the year 270, due to the conflict between Queen Zenobia of Palmyra and the Emperor Aurelian, that in order to contain the rebellion of the people, he set fire to the royal district of Alexandria. Also in the year 391, bishop Theophilus ordered, according to tradition, a destruction that probably affected the Serapeion. However, its complete destruction came when in 646 AD, Alexandria was invaded and occupied by the Muslims, it was then when what remained of that great library, was looted and destroyed by order of Amir Amr ibn al-As.