The majority of Egyptologists agree on the outline and many details of the chronology of Ancient Egypt. This scholarly consensus is the so-called Conventional Egyptian chronology, which places the beginning of the Old Kingdom in the 27th century BC, the beginning of the Middle Kingdom in the 21st century BC and the beginning of the New Kingdom in the mid-16th century BC. Despite this consensus, disagreements remain within the scholarly community, resulting in variant chronologies diverging by about 300 years for the Early Dynastic Period, up to 30 years in the New Kingdom, and a few years in the Late Period. In addition, there are a number of "alternative chronologies" outside scholarly consensus, such as the "New Chronology" proposed in the 1990s, which lowers New Kingdom dates by as much as 350 years, or the "Glasgow Chronology" (proposed 1978–1982), which lowers New Kingdom dates by as much as 500 years. Overview Scholarly consensus on the general outline of the conventional chronology current in Egyptology has not fluctuated much over the last 100 years. For the Old Kingdom, consensus fluctuates by as much as a few centuries, but for the Middle and New Kingdoms, it has been stable to within a few decades. This is illustrated by comparing the chronology as given by two Egyptologists, the first writing in 1906, the second in 2000 (all dates in the table are BC). The disparities between the two sets of dates result from additional discoveries and refined understanding of the still very incomplete source evidence. For example, Breasted adds a ruler in the Twentieth dynasty that further research showed did not exist. Following Manetho, Breasted also believed all the dynasties were sequential, whereas it is now known that several existed at the same time. These revisions have resulted in a lowering of the conventional chronology by up to 400 years at the beginning of Dynasty I. Regnal years Forming the backbone of Egyptian chronology are the regnal years as recorded in Ancient Egyptian king lists. Surviving king lists are either comprehensive but have significant gaps in their text (for example, the Turin King List), or are textually complete but fail to provide a complete list of rulers (for example, the Abydos King List and the Palermo Stone), even for a short period of Egyptian history. The situation is further complicated by occasional conflicting information on the same regnal period from different versions of