Matthew 23:32
Fill ye up then the measure of your fathers.
That is what was in her cup, all the blood which was shed upon the earth.
Jesus told us who exactly were those who did this, it wasn't sometime in the 4th century. Because Jesus tells us what generation it was, That upon you may come all the righteous blood shed upon the earth, from the blood of righteous Abel unto the blood of Zacharias son of Barachias, whom ye slew between the temple and the altar. Verily I say unto you, All these things shall come upon this generation. That's pretty plain, Jesus is telling us who Mystery Babylon is, and when she was living.