August 1: On August 1st year 527, King Justinian assumed as the sole ruler of the Byzantine Empire.

Many people have been confused with the names of "Byzantine Empire and Eastern Roman Empire". For it is the same thing! 

Actually, the Byzantine Empire was the eastern Greek-speaking part of the Roman Empire. Roma fell to the barbarians of King Odoacer Heruli in the year 476. That is to say 51 years previously to the foundation of the Eastern Roman Empire in what was known as Byzantium, an ancient Greek colony. 

The Roman Empire was divided in AD 395 into two parts. The Western half, ruled from Rome, fell to the tribal Germanic peoples in the 5th century. The Eastern half, known as the Byzantine Empire, lasted for more than 1,000 years. Until the mid-11th century, when it began to decline in power, the Byzantine Empire was one of the leading civilizations in the world.

So today we speak of the Western Roman Empire, which fell into the hands of the barbarians, being Romulus Augustus the last Roman emperor, based in Rome.

On the other hand, the Eastern Roman territory had its capital at Constantinople, now Istanbul, Turkey. King Constantine (Roman) rebuilt the city of Byzantium and re-called it Constantinople on his behalf. 

Justinian I – r. 527-565. Born a peasant in Illyricum, he joined & was adopted by Justin in Constantinople & was well educated. He was active during his uncle’s reign. He became emperor in 527 at Justin’s death. He promoted himself as “the Emperor who never sleeps”. He married Theodora after changing the law preventing patricians from marrying outside their class. He promoted the Blue faction. When Justinian was crowned, he had Theodora crowned at the same time, & treated her as an equal.

Then, from there on, Romans began to speak of the Byzantine Empire to the eastern part of the Roman Empire. The Eastern Roman Empire or Byzantine Empire lasted until 1453 when the Ottoman Turks took Constantinople and made it their capital in the name of Istanbul.

The Baptism of Constantine painted by Raphael's pupils (1520–1524, fresco, Vatican City, Apostolic Palace); Eusebius of Caesarea records that (as was common among converts of early Christianity) Constantine delayed receiving baptism until shortly before his death.

Justinian known as "The Great," was the emperor of the Byzantine Empire from 527 to 565; that is, he ruled for 38 years.

Justinian tried to recover all the territories of the Eastern Roman Empire and more. In Rome they spoke in Latin, but in Constantinople, Byzantine Greek was spoken.

Justinian was a prolific builder: The church of San Vitale in Ravenna with precious mosaics; the Hagia Sophia, which became the world's largest to date mosque. Byzantine art was generously supported by religious mosaics, sculptures, paintings, as well as architecture.