When Did Christendom Begin?

Canadian theology professor Douglas John Hall dates the 'inauguration of Christendom' to the 4th century, with Constantine playing the primary role (so much so that he equates Christendom with "Constantinianism") and Theodosius I (Edict of Thessalonica, 380) and Justinian I secondary roles.

When did Christendom happen?

By the 10th century the religious and cultural community known as Christendom had come into being and was poised to enter a prolonged period of growth and expansion. Important progress had taken place well before this period, however.

When did modern Christianity begin?

The history of modern Christianity concerns the Christian religion from the beginning of the 15th century to the end of World War II. It can be divided into the early modern period and the late modern period.