Dark Ages is a term of historical periodisation used to refer to a period of supposed cultural and economic deterioration, and scarcity of written record, usually being contrasted with the more recent times of the writer and with classical antiquity. Its original use referred to the Western European Middle Ages (roughly the 6th to 14th centuries), emphasising the perceived decline following the fall of the Roman Empire. Wikipedia, Dark Ages

"In the battle of civilization for body-supremacy over Mind, it may well be that the moral, mental and spiritual decline of the last fifty years will continue into another degrading Dark Age." [Atomic Suicide, page 174]