The dark ages traditionally refers to the period in Western Europe between the collapse of the Western Roman Empire in the 5th century roughly until the crowning of Charlemagne in the year 800. Though I've also seen it refer as extending to the Scholastic Period when classical literature was re-introduced into Western Europe by the Arabs.
"The Dark Ages" were so-called because for a very long time there was little documentation of the period. This is the same reason why historians speak of the "Greek Dark Ages", the few centuries prior to Homer where there is scarce historical documentation, and thus we are largely in the dark.
Since historians today (and for a rather long time now) have a pretty solid grasp on the history of the period, the term "Dark Ages" is generally considered antiquated and archaic; it simply isn't an accurate descriptor of the period since the period isn't dark, we know what was going on in the period, and there is plenty of source material to work with.
Any other definition of "The Dark Ages" isn't worth considering since it has nothing to do with the discipline of historians. Your personal opinion on the matter is, to put it bluntly, moot. Historians deal in facts, not truthiness.
-CryptoLutheran