At the urgent request of his friend
George Syncellus, Theophanes undertook the continuation of Syncellus's
Chronicle (, Chronographia), during the years 810 to 815. The language used occupies a place midway between the stiff ecclesiastical and the vernacular Greek. He made use of three main sources: first, material already prepared by Syncellus; second, he probably made the use of a set of extracts made by
Theodore Lector from the works of
Socrates Scholasticus,
Sozomenus, and
Theodoret; and third, the city chronicle of Constantinople. Cyril Mango has argued that Theophanes contributed but little to the chronicle that bears his name, and that the vast bulk of its contents are the work of Syncellus; on this model, Theophanes's main contribution was to cast Syncellus's rough materials together in a unified form. Theophanes's part of the chronicle covered events from the accession of
Diocletian in 284 (which is the point where the chronicle of
George Syncellus ends) to the downfall of
Michael I Rhangabe in 813. This part of the chronicle is valuable for having preserved the accounts of lost authorities on Byzantine history for the seventh and eighth centuries that would otherwise have been lost. The work consists of two parts, wherein the first provides a chronological history arranged per annum, and the second contains chronological tables that are regrettably full of inaccuracies. It seems that Theophanes had only prepared the tables, leaving vacant spaces for the proper dates, but that these had been filled out by someone else (
Hugo von Hurter,
Nomenclator literarius recentioris I, Innsbruck, 1903, 735). In the chronological first part, in addition to reckoning by the years of the world and the Christian era, Theophanes introduces in tabular form the regnal years of the Roman emperors, of the Persian kings and Arab caliphs, and of the five ecumenical patriarchs, a complex system which sometimes leads to considerable confusion. The first part, though lacking in critical insight and chronological accuracy, greatly surpasses the majority of Byzantine chronicles. Theophanes's
Chronicle is particularly valuable beginning with the reign of
Justin II (565), as in his work, he then drew upon sources that have not survived his times Theophanes's
Chronicle was much used by succeeding chroniclers, and in 873–875 a
Latin compilation was made by the
papal librarian
Anastasius from the chronicles of
Nicephorus, George Syncellus, and Theophanes for the use of a deacon named Johannes in the second half of the ninth century and thus was known to Western Europe. There also survives a further continuation, in six books, of the
Chronicle down to the year 961 written by a number of mostly anonymous writers (called
Theophanes Continuatus or
Scriptores post Theophanem), who undertook the work at the instructions of
Constantine Porphyrogenitus. Theophanes was the first to claim that the Prophet of the Islamic religion
Muhammad had
epilepsy. ==Notes==