Palermo Stone
According to Toby Wilkinson's study of the Palermo Stone in "Royal Annals of Ancient Egypt", this near contemporary 5th dynasty document assigns Khasekhemwy a reign of 17.5 or nearly 18 full years. Wilkinson suggests that a reign of 18 "complete or partial years" can be attributed to Khasekhemwy since the Palermo Stone and its associated fragments record Years 3-6 and Years 12-18 of this king and notes that his final year is recorded in the preserved section of the document.