Medieval Christians lacked any accurate chronology of Muhammad’s life

Evidence

The absence of authentic detail, except what derived from the Risalah, meant in most cases a complete ignorance of the historical sequence of Muhammad’s public career. Only a very few authors were able to distinguish even the Meccan and Medinan periods in his life, and his final triumph, after the agreement at Hudaybiyah, seems to have been mentioned by, perhaps was known to, none. There simply did not exist in this period a straightforward chronological account of the whole of Muhammad’s life which was anything like accurate. — Norman Daniel, Islam and the West, 537