In the Roman Empire of the 4th century, the Ludi Triumphales ("Triumphal Games") were games (ludi) held annually September 18–22 to commemorate the victory of Constantine over Licinius at Chalcedon in 324. No description of these games has survived, but they are significant in the historical transformation of Roman religious and state institutions under the Christian emperors, an era inaugurated by the conversion of Constantine. Forty-eight circus races (ludi circenses) are recorded for September 18, which was also celebrated as the birthday (dies natalis) of the emperor Trajan.