The lengths of the reigns of Senusret II and Senusret III are one of the main considerations for discerning the chronology of the Twelfth Dynasty. The Turin Canon is believed to assign a reign of 19 years to Senusret II and 30 years of reign to Senusret III. This traditional view was challenged in 1972 when the American Egyptologist William Kelly Simpson observed that the latest attested regnal year for Senusret II was his 7th, and similarly for Senusret III his 19th.