Today is the date given for the publication of the edict of Milan in 313, so today marks the 1700h anniversary.
The facts are,however, a little more complicated than that statement of facts. The Emperors Constantine and Licinius had met at Milan earlier in the year and agreed on a policy of toleration for Christians within their portions of the Roman Empire. Today's anniversary is of the publication at Nicomedia on June 13 of the agreement already made. Whereas Constantine was clearly favourable to Christianity in his westernmost part of the Empire, Licinius himself was a pagan, and what he published for his territories in the Balkans was not an edict as such but a letter notifying his officials of the policy. The text is preserved in Lactantius, and was issued after the defeat of the aggressively pagan Maximian Daia.
Image: ISTORAX on Flickr
It is not clear if there was an official "Edict of Milan" at all. What was notified was the establishment of freedom of religion and to worship for Christians and also for others, and restores civil rights and property. There is an online account of the background and discussion of the issues here.
Licinius himself, of whom there is an online biography here, may possibly have converted to Christianity, but was to be defeated and deposed by Constantine in 324, and hanged in 325 for conspiring against his former colleague. Constantine was left as the ruler of the entire Empire.
Emperor Constantine the Great