The Byzantine Empire did not use heraldry as the Western Europeans did. For this reason, the Eastern Roman Empire did not have an official flag until after the marriage of Charlemagne and Irene. Even then, the Byzantines were not known for flying flags well into the 9th century. However, the Labarum symbol has been consistently synonymous with the Byzantine Empire, leading to the common misconception that it was, in fact, a flag of the Byzantine Empire.