Around 748 BC. Titus Tatius introduced the sun god to Rome. It fit in with the many gods and cults. Around 50 AD. CIRCUS MAXIMUS was used for SOL worship, an event. In 274 AURELIAN made SOL INVICTUS more instituted and founded a college for leaders of SOL worship.
SOL INVICTUS, was on coins, images and highly worshiped. *In 321 COMSTANTINE made a LAW - DAY OF THE SUN - [the official day of rest]*. Sunday was the day to honor SOL INVICTUS and JESUS. Jesus was brought into the fold, with SOL and the other cults and gods.
Constantine before a battle, had a vision in the sun of a cross. Somehow, I feel equated Jesus and the sun. Equating Son of God, Son of Man, maybe sun and son, but JESUS was in the fold with SOL INVICTUS. *Sunday was by ROMAN LAW* the day to worship SOL INVICTUS and JESUS. Who was to tell Rome any different ?
It is interesting in the New Testament, that there is an Epistle to TITUS. The same first name as Titus Tatius, the man who introduced SOL to Rome. Not to mention the Epistle of Romans. Maybe an omen of GOD or a message to note ???????