Were not so dark and no where near as long as popular knowledge has it.
First off, very few historians actually use the term anymore. When they do it is really limited to the collapse of western Roman political authority in Western Europe from circa 450 AD to circa 850 AD. For the most part in the East (where most of the population was), under the Byzantine Empire, Roman political structures and culture continued unabated until the fall of Constantiople in the 15th century. From circa 850 on, the West had improved its political and military power enough that it was either was able to fight off invaders (like the Muslims at Tours) or incorporate them into their culture (Norsemen became Normans). It is really REAALY out of date to conflat the "Dark Ages" with the entirety of the Middle Ages and say things only got significantly better with the "Renaissance"
What did stop for a time in the West was classical literary culure of Rome and Greece--but technology and knowledge in all sorts of human endeavors improved and spread throughout the "darkest" of the post-Roman period--so much so, I really have to refer you to the works of Rodney Stark, especialy How the West Won