 Much more lasting than the ephemeral month names of the post-Augustan Roman emperors were the Old High German names introduced by Charlemagne.According to his biographer, Charlemagne renamed all of the months agriculturally into German.These names were used until the 15th century, over 700 years after his rule, and continued, with some modifications, to see some use as "traditional" month names until the late 18th century.