Abstract
It is most unusual for a detailed literary account of political events to have survived which enables modern scholars to study the course of Sasanian history almost day by day. Interpretation of the History of Theophylact Simocatta has led to the mis-dating of Khusrau II's accession to the throne to 15 February 590. The existence of extensive issues of silver drachms struck by Hormizd IV, Khusrau II and Varhran VI during the period 590–1 and of Khusrau II in 627–8, alongside a re-examination of the sources, enables the date to be corrected to soon after 27 June (New Year) 590.