A difficult question to answer.
The dark ages took a rather long time to end; not all at once. The age of enlightenment could arguably be traced back to Guttenburg and the invention of the movable type printing press. Others may source equally valid starting points.
I would qualify the age of enlightenment as starting when scientific inquiry began to become more important than the dogma of the church. People began to throw off the shackles of mind control and started trying to figure out the world for themselves.
I cannot pin down anything like an exact date, as this was an organic process over decades if not centuries of time.
It is difficult to imagine how far advanced we might be right now; perhaps travelling to other stars, perhaps having cures for all major causes of death, had we not been hobbled for over a thousand years by religion.
