Let's see: the Emperor Augustus was the first to inherit the title of pontifex maximus, waaay back during the Principate. The Emperor Gratian (367-383) renounced the title of pontifex maximus during his rule, becoming, as my source states, "the first emperor in almost four centuries to refuse the office that brought with it control of the ROMAN STATE RELIGION." (H. A. Drake, _Constantine and the Bishops_, p.403).
Augustus' rule ended in AD 14. Constantine reigned from AD 306 to 337. Gratian, once again, ruled from AD 367 to 383. Since the Imperial office of Pontifex Maximus was assumed with Augustus and abandoned with Gratian, and Constantine ruled between the two, then Constantine was Pontifex Maximus of the Roman State Religion. QED.
And, wagglebee, what WAS the Roman State Religion in AD 325, when Constantino il Grande summoned the Council of Nicea?
I'm not quite sure about the point that UriÂel-2012 was making about Easter, but on this matter of fact he's right. You -- and others -- owe him an apology.
Not even remotely.
The fact that Constantine made Christianity the official religion of the Roman Empire DID NOT make him head of the Church. You can find well-documented lists of Catholic popes on the internet, NONE of them will ever list Constantine as a pope. In 325, His Holiness Sylvester I was pope.
I'm not quite sure about the point that UriÂel-2012 was making about Easter,
Keep digging, you'll figure it out.