"Constantine made it illegal to not celebrate "Apollo Day," which in Rome was the "Sun + day." Ever notice that when you walk out of a "church" on that day the sun is directly overhead? That is 12PM, when Apollo can see you best when you are leaving "his house" on "his day." Why? Because Apollo needed to see it. You mean Apollo could not see inside your heart? Nope. That was why Jesus said that God can see you in your closet (Matt 6:6). Before Jesus' day people generally believed that you had to go to a special place, to see a special guy, do some kind of special ceremony, for God to be see it and accept it. 

Apollo Day was Roman custom, but kit was made law after 321 AD. Constantine wanted his soldiers to have one day where they didn't have to build, but he also wanted them in one place so he could collect taxes."

Good research, I did some work like this a while back and put it in a book that we published, so I understand the effort given. So few know our story, and more get exposed all the time. The "church" machine has made all Christian things more complicated than it needs to be. If friends can gather together for pie and ice cream, then a fellowship can be started.