Here are a couple of paragraphs from my second book:
In 312, Constantine defeated and killed his rival Maxentius, son of Maximian, and he became emperor of the west. He, like his father, favored Christianity. Constantine had a vision of a burning cross right before his battle with Maxentius. Above the cross were the words En Hoc Signo Vinces, which means “In this sign conquer.” He therefore fought the battle in the name of the Christian God. His victory caused him to convert to Christianity. In 313, Constantine issued the Edict of Milan, giving Christians the right to practice their religion. He urges his followers to become Christians, like him. In 321, Constantine issued an edict forbidding work on Sunday. In 323, he defeated the eastern emperor; and became the sole emperor of the east and west.
In 324, he established Christianity as the state religion. Finally, all of Rome accepted Christianity as their state religion. But at this time, there were many different doctrines among Christians. So Constantine called upon a conclave of bishops from all over Rome, to settle these differences. This happened at the Council of Nicea in 325, which was convened to solve two main differences: The first was the divinity of Christ. Arius, a priest of Alexandria, was teaching that Christ was created and not eternal and divine like the Father. The Council denied him and his doctrines; and condemned his followers, the Arian teachers, although this Arian wing continued strong in some areas. When the Germanic and Gothic invaders were converted to Christianity, it was usually to the Arian form. The other major difference, facing the Council was the date on which to celebrate Passover. At this time, in Asia Minor, many Christians still commemorated Jesus’ death on the day the Jewish Passover lambs were slain. But Rome and the Western churches chose to honor the resurrection instead. They celebrated the Passover always on a Sunday. The Council ruled in favor of the west and Rome. It ruled that the Passover, commemorating the death of Jesus, no longer be kept—anyone keeping the old way would be put to death. This new Passover was celebrated on the first Sunday after the full moon following the vernal equinox. It was later called “Easter” by the Germanic Christian converts. But was this so called “Christianity” the real deal; or was it a false, counterfeit version? The first thing Constantine did was to substitute Sunday for the sabbath, instead of the seventh day that should have been. He did this in hopes of attracting the sun worshipers of his day. Remember how I pointed out in chapter three that the seventh-day sabbath was a “sign” commandment? This true sabbath pointed to God’s true covenant people. The Roman Catholic Church grew out of this “hijacking” of Christianity by Constantine. I might note here: as a result of this hijacking—and his Sunday sabbath—the later Council of Laodicea (AD 365) outlawed the true seventh-day sabbath (sunset Friday to sunset Saturday).