Were Charlemagne and Harun al-Rashid alive at the same time?
Yes. Charlemagne and Harun al-Rashid were alive at the same time for 43 years, from AD 766 to AD 809.
Charlemagne
King of Franks, regarded as the first Holy Roman Emperor (747–814)
Born AD 740–748 · died 28 January AD 814