Egyptian chronology
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.