You've obviously confused Augustine, the Catholic bishop of the North African town of Hippo, the "Doctor of Grace", with Constantine, the Roman Emperor, who was certainly friendly to Christianity but may or may not have died an Arian heretic rather than a Catholic.
They aren't the same person, not even close.
Christians were worshipping on Sunday long before Constantine. Even some of the SDAs admit that now. Ignatius of Antioch, writing in AD 110, congratulates some of those to whom he was writing on "no longer Sabbathing". Justin Martyr (AD 150) and others write of Christians meeting for worship "on the first day of the week, the day named for the sun".
Read the two Babylon's and your eyes will be opened as to the parallels of the Babylonian religion and the RCC.
An awesomely stupid and wrong book, based on poorly-understood 1840's archaeology, glued together with one logical fallacy after another.
Ralph Woodrow is a Baptist who wrote a book endorsing Hislop's idiocy. Then a fellow Baptist challenged him to look at it more closely, and he began to see the errors all over Hislop's book. He wrote another book, The Babylon Connection, exposing and explaining those errors. I suggest you read it.
“You’ve obviously confused Augustine, the Catholic bishop of the North African town of Hippo, the “Doctor of Grace”, with Constantine”
You say tomato i say tomato