Egyptian chronology

Egyptian chronology is the study of events in Ancient Egypt and trying to date when they took place. There is a general agreement about the correct chronology among Egyptologists. The Old Kingdom began in the 27th century BC, the Middle Kingdom in the 21st century BC, and the New Kingdom in the mid-16th century BC.
However, some details are still disputed. The dates for the Early Dynastic Period can vary by up to 300 years, those of the New Kingdom by up to 30 years, and those if the the Late Period by up to a few years.
Some individual Egyptologists have come up with alternative chronologies. For example, the "New Chronology," which was proposed in the 1990s, changes the New Kingdom dates by 350 years, and the "Glasgow Chronology," which was proposed from 1978 to 1982, changes the New Kingdom dates by 500 years.
Overview
Agreement on the general chronology used in Egyptology has not changed much over the last 100 years. For the Old Kingdom, there have been changes by as much as a few centuries. The Middle and the New Kingdoms dates have changed by only a few decades. The changes can be seen by comparing the chronology of two Egyptologists, the first from 1906 and the second in 2000 (all dates in the table are BC).
There are differences between the two sets of dates because of new discoveries and a better understanding of what is already known. For example, in Breasted's 1906 list, he added a ruler in the Twentieth dynasty that further research would show did not exist. Using Manetho writings, Breasted also believed that each new dynasty followed the old one in a sequence. It is now known that several dynasties existed at the same time. Those changes changed the chronology by 400 years at the beginning of Dynasty I.
Regnal years
The main way to work out the chronology is to use the ancient Egyptian lists of kings. The number of years that each king ruled, the regnal years, can be added up. However there are problems with the lists. Some, such as the Turin King List, are quite detailed but are incomplete. The whole of Abydos King List has survived, but it is a complete list of rulers. Sometimes, various versions of the same text are different. For example, Manetho's history of Egypt has not survived. Later writers such as Eusebius and Sextus Julius Africanus used Manetho's work for their histories, but their dates for the same ruler are often very different.
The dates for king's rule can be pieced together from inscriptions. They often give a date in the form of the regnal year of the ruling pharaoh. They may or may not include any coregencies with a predecessor or successor. Some Egyptian dynasties may have overlapped, with different pharaohs ruling in different regions at the same time. That may lead to widely-different chronologies.
Egyptologists have two other ways to find the total number of years. For the Old Kingdom, they can use the number of cattle censuses. For later periods, they can use the celebration of a sed festival. In the Old Kingdom, there was a regular census at which the number of cattle was counted. At first, it was believed to have taken place every two years. There were 24 cattle censuses during the rule of Sneferu, who therefore ruled for 48 years. However, new research has shown the census was sometimes held every year or after gaps of more than two years. The sed festival was held on the 30th anniversary of the Pharaoh's rule. A ruler with one sed festival recorded would have ruled at least 30 years. However, that may not have been the practice in all cases.
Linking to other events
A useful way to work around those gaps in knowledge is to find links to other known events, which can lead to a precise date. A number of them have been found, but they are of varying degrees of usefulness and reliability.
Archeological sequences
This is using archeaology to put events in order, or a sequence. It does not fix a person or event to a exact year. A series of events can provide evidence to provide or support a precise date. For example, a number of stone vessels of the rulers of the first two dynasties were placed in rooms under the Step Pyramid of Djoser. They were sealed off by during the building of the pyramid during the Third Dynasty. Another example is stone blocks from the Old Kingdom with the names of several kings. Thee stones were later used to build the Middle Kingdom pyramid-temples at Lisht. The third pylon at Karnak, built by Amenhotep III had "fill" material from the kiosk of Sesostris I, as well as stelae of the Second Intermediate Period and the Eighteenth Dynasty of the New Kingdom.
Other chronologies
The chronologies of other cultures can be used to find links to Egypt. The most important are the Assyrian and Babylonian chronologies. Allo, chronologies of the Hittites, ancient Palestine, and ancient Greece are also used. For example, in the 18th century BC, a stela of the governor of Byblos Yantinu stated that Pharaoh Neferhotep I ruled at the same time as Kings Zimri-Lim of Mari and Hammurabi of Babylon. In the 15th century BC, during the Amarna Period, there are letters between Egyptian Kings Amenhotep III and Akhenaten and various Near Eastern monarchs.
Inscriptions
Inscriptions on objects often provides clues. The burial of Apis bulls began in the reign of Amenhotep III. They were killed in a sacrifice and placed in tombs. Details of each bull were included, as well as details of the rulers. It is possible to estimate dates of regnal years using that information. The bulls were still being buried in Ptolemaic times. There is a significant gap in the record between Ramesses XI and the 23rd year of Osorkon II. Poor documentation of the finds in the Serapeum also makes it difficult to use these records.
Astronomy
Astronomy can also provide clues for dates. The best known of them is the Sothic cycle. A study of that led Richard A. Parker to argue that the dates of the Twelfth dynasty could be fixed exactly. New research does not always agree with the information that is used in to work out dates that way. For example, Donald B. Redford, in attempting to fix the date of the end of the Eighteenth dynasty, did not use the Sothic evidence. Instead he used links between Egypt and Assyria by way of the Hittites and help from astronomical observations.
Radiocarbon dating
Radiocarbon dating is another way to work out dates. It is useful for the Early Dynastic period for which other methods have dates as different as 400 years. A 2013 study put the start of the First dynasty in the 32nd or 31st century. That matches other information, which places it in between the 34th and 30th centuries.
Minoan eruption
The Minoan eruption is a problem for both Egyptian and Aegean (Minoan) chronology. The radiocarbon date for the eruption is between 1627 and 1600 BC. The date used in archaeology is c. 1500 BC. That date is important in the study of the civilisations in the Eastern Mediterranean. Since 2012, there have been suggestions that the answer would be to change both dates towards a "compromise" date in the mid-16th century BC. As of 2014, the problem has not been satisfactorily resolved.
Dendrochronology
Dendrochronology uses patterns found in tree growth rings to work out a date. That is possible for Egyptian chronology. An example is the Uluburun shipwreck, which is from the New Kingdom. By using both dendrochronology and radiocarbon dating, tree rings can be dated as far back as the Middle Kingdom. That was used for the coffin of Ipi-ha-ishutef (dated 2073+-9 BC) and the funerary boat of Senusret III (dated 1887+-11 BC; the conventional reign date is 1878 BC-1839 BC).
Alternative chronologies
A number different chronologies were presented during the 20th century:
The Revised Chronology of Immanuel Velikovsky, as explained in his Ages in Chaos series.
The chronology of Donovan Courville, as described in The Exodus Problem and Its Ramifications.
The Glasgow Chronology, which was developed by members of Velikovsky's Society for Interdisciplinary Studies in 1978.
The New Chronology of David Rohl, as described in his Test of Time series.