Edited sentence: Although Professor Heinrich Otten has called the current scholarly consensus a "rubber chronology" that could be stretched or shrunk, by arbitrarily established lengths of co-regencies between rulers and even overlapping dynasties, the outlines and dates have not fluctuated very much in the last 100 years.Establishing a chronology for the ancient Near East relies on using a combination of various ancient King lists and searching for chronological synchronism with events whose dates are known.The fact that no single ancient source provides a complete list of rulers makes matters worse, and a single ancient source (such as Manetho's history of Egypt) can even contradict itself by coming to us only through a variety of intermediary sources.The largest changes from 100 years ago are in the Old Kingdom period.This is complicated by the fact that the ancient Egyptians used no single system of dating, and that the length of their reigns is often not accurately known, especially where interregnums or coregencies are involved