the dark ages

noun
1
the period of European history between the end of the Roman Empire and the end of the 10th century AD
عصر تاریکی, دوران تاریک
2
a period of history or a time when something was not developed or modern
دوران تاریک, دوران عقب‌ماندگی, قرون تاریک
Back in the dark ages of computing, in about 1980, they started a software company.
You’re living in the dark ages, Mum!