Constantine Timeline
Timeline Description: Constantine (272 - 337 CE), also known as Constantine the Great or Constantine I, was an emperor of the Roman Empire. He is most noted for his official conversion to Christianity and the shift of power in the empire to the east, which began the empire's transformation into the Byzantine Empire.

Date Event
272 BC Constantine is born(c. February 27, 272 CE).

Constantine is born Flavius Valerius Constantinus in the city of Naissus around February 27, 272. His father, Flavius Constantius, is a skilled politician, soldier, and bodyguard to Emperor Aurelian. His mother, Helena, is of low social rank.
293 Constantius is made Caesar under Emperor Diocletian(March 1, 293).

By 293, the empire is ruled by two co-emperors, called Augustus, and each has two junior rulers under them, called Caesar. Diocletian, the eastern Augustus, appoints Constantine's father, Constantius, to Caesar on March 1 and immediately sends him off to battle rebels in Gaul. This sets up Constantine as Constantius's heir to the role of Caesar. Constantine stays in Diocletian's court in Nicomedia to act as a hostage to ensure his father's loyalty.
303 Constantine witnesses the "Great Persecution."

In 303, Constantine returns from an eastern military campaign to Nicomedia in time to witness Diocletian executing the "Great Persecution." Based on instructions from the oracle of Apollo at Didyma, Diocletian persecutes all Christians under his rule. He has churches and scripture burned, Christians deprived of rank, and priests jailed. Constantine remains neutral during the Great Persecution.
305 Diocletian and Galerius concurrently abdicate as emperors(May 1, 305).

Due to sickness and political pressure, both Diocletian and Galerius abdicate their roles as Augusti on May 1, 305. Galerius is named Augustus in the east, and Constantine's father, Constantius, is named Augustus in the west. Constantine is forced to flee to his father's protection to avoid becoming a hostage in Galerius's court.
306 Constantius dies(July 25, 306).

After fleeing Galerius, Constantine joins his father on campaign in Britain. However, his father falls sick during the campaign and dies on July 25, 306. He names Constantine his heir as Augustus, and Gaul and Britain support his rule - though Iberia, which has only recently been conquered, does not. Galerius is outraged by the news, but he is forced to compromise and grants him the title of Caesar. Constantine accepts to solidify his claim. He is granted control over Britain, Gaul, and Spain.
306 Maxentius rebels against Constantine(October 28, 306).

Outraged by Constantine's power, a political rival named Maxentius seizes the title of emperor and starts a civil war in Rome on October 28, 306. Galerius neither recognizes him nor moves against him. Constantine sends an army against him, but since the soldiers served under Maxentius's father, they defect to the rebel's side.
307 Constantine marries Fausta, Maxentius's sister.

Maximian, Maxentius's father, comes out of retirement to approach Constantine with a compromise. Constantine agrees to marry Maxentius's sister, Fausta, and be promoted to rank of Augustus. In exchange, he recognizes Maxentius and offers him no military support. Constantine's refusal to fight makes him popular with the people.
308 Galerius calls a council to resolve the dispute(November 11, 308).

Galerius calls a council at Carnuntum on November 11, 308 to resolve the western dispute for power. Diocletian returns from retirement, and Galerius and Maximian attend as well. Maxentius is forced to resign, and Constantine is demoted back to Caesar - though he refuses to recognize the change and continues to fashion himself as Augustus.
311 Galerius ends the persecutions of Christians(April 30, 311).

Galerius falls ill in 311, and as his last act in power, sends a letter that restores religious freedom to Christians. However, he soon dies thereafter. This sets off a war between Constantine and Maxentius, who barricades himself in Rome.
312 Constantine takes the sigil of the Christian cross in battle(October 28, 312).

Maxentius, still in Rome, finds himself politically unpopular and worries that he won't be able to defeat Constantine during a long siege. He marches north to meet him at the Battle of the Milyain Bridge, during which Constantine's forces famously take on the sigil of the Christian cross. This signals his conversion to Christianity. Constantine defeats Maxentius, who is killed in the battle, and enters Rome to great celebration. The Senate names him Augustus.
313 Constantine agrees to the Edict of Milan(February 313).

Constantine moves to solidify his power and meets with one of his few remaining rivals, Licinius, in February 313. Licinius agrees to marry Constantine's half-sister, Constantia, and both men agree to the Edict of Milan, which grants full tolerance to Christianity and all other religions in the Empire.
324 Constantine wins the Battle of Chrysopolis(September 18, 324).

Peace is short-lived as Licinius starts reneging on the terms of the Edict of Milan, and attempts at negotiation ultimately dissolve into war. Licinius represents the older, pagan way of things, and Constantine marches under the standard of the labarum, a symbol of Christianity. Constantine defeats Licinius in the Civil War of 324 at the Battle of Chrysopolis on September 18. This makes him the sole emperor of Rome.
325 Constantine begins the First Council of Nicea(May 20, 325).

Constantine calls the First Council of Nicea, in what is modern day Turkey, on May 20, 325. He hopes to unify Christian doctrine, particularly around the issue of Arianism, or the question of whether Jesus is superior or equal to God. The influential Nicene Creed is formed.
330 Constantine renames Byzantium Constantinople(May 11, 330).

After defeating Licinius, Constantine signals the shift from the old Greek and pagan ways to the Roman and Christian powers, and he moves his capital to finalize the change. After considering many different cities for the new capital, he chooses Byzantium for its logistical and strategic importance and renames it Constantinople. This signals the shift of the Roman Empire towards the East.
337 Constantine dies(May 22, 337).

After solidifying the empire and instituting political and economic reforms, Constantine is finally baptized as a Christian shortly before dying on May 22, 337. He is buried in Constantinople and succeeded by his son from Fausta, Constantine II.