Chronological synchronism is an event which links two chronologies. For example, it is used in Egyptology to ground the Egyptian chronology. The main types of chronological synchronism are synchronisms with other historical chronologies, and synchronisms with precisely datable astronomical events.
Synchronisms with other chronologies often rely on some form of recorded communication between regions. For example in Egyptology, the earliest such synchronisms appear in the 15th century BC, during the Amarna Period, when we have a considerable quantity of diplomatic correspondence between the Egyptian Kings Amenhotep III and Akhenaten, and various Near Eastern monarchs, linking Egyptian chronology with other Near Eastern chronologies.
Astronomical synchronisms rely on precise identification of astronomical events recorded in the historical record. The best known of these is the Sothic cycle, and careful study of this led Richard A. Parker to argue that the dates of Egypt's Twelfth dynasty could be fixed with absolute precision. More recent research has eroded this confidence, questioning many of the assumptions used with the Sothic Cycle, and as a result experts have moved away from relying on this Cycle.
- Set forth in "Excursus C: The Twelfth dynasty" in his The Calendars of ancient Egypt (Chicago: University Press, 1950).
- One example is Patrick O'Mara, "Censorinus, the Sothic Cycle, and calendar year one in ancient Egypt: the Epistological problem", Journal of Near Eastern studies, 62 (2003), pp. 17-26.