The term "Constantinian" refers to the period and policies associated with the Roman Emperor Constantine the Great, who ruled from 306 to 337 AD. This era is marked by significant changes in the Roman Empire, particularly the promotion of Christianity as a favored religion. Constantine's Edict of Milan in 313 AD granted religious tolerance, allowing Christians to practice their faith openly. Additionally, the Constantinian era is known for the establishment of Constantinople (modern-day Istanbul) as the new capital of the Roman Empire. This strategic city became a center of trade and culture, influencing the development of both the Eastern and Western Roman Empires.