Dark Ages

"Dark Ages" is a term for the period in European history from the fall of the Roman Empire in 476 to circa 1000, where there is a perception of little intellectual development culturally and the few surviving records of what happened still leave a lot of things unanswered.

You may be interested in the following pages:

See also:
  • Dork Age, a period in a franchise where a dramatic change of direction or style failed to gain traction with the audience

http://tvtropes.org/pmwiki/pmwiki.php/Main/DarkAges