the dark ages
noun /ðə ˈdɑːk eɪdʒɪz/
  /ðə ˈdɑːrk eɪdʒɪz/
 [plural]- the Dark Agesthe period of European history between the end of the Roman Empire and the end of the 10th century ADTopics Historyc2
 - (often humorous) a period of history or a time when something was not developed or modern
- Back in the dark ages of computing, in about 1980, they started a software company.
 - You’re living in the dark ages, Mum!