Edict of Milan, A.D. 313
Christianity suddenly advanced under Emperor Constantine and the Edict of Milan, A.D. 313, allowing the New Testament books to be spread to the East. He assigned Eusebius to prepare 50 copies of the Divine Scriptures, effectively establishing a standard that legitimized all formerly disputed books.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. The Canon of the New Testament by Milton C. Fisher, Pages 74-75.)