epoch-making
From Longman Dictionary of Contemporary Englishepoch-makingˈepoch-ˌmaking adjective CHANGE/MAKE something DIFFERENTvery important in changing the way people live or the way a society is organized the epoch-making social changes of the 1960sExamples from the Corpusepoch-making• But then a truly epoch-making change in public attitudes took place.• an epoch-making event• It is indeed rare for the participants in such epoch-making events to have a complete understanding of them and their consequences.• This period of upheaval was to have an epoch-making impact upon the whole structure of Muscovite society.• This thrilling epoch-making race Was by agreement taking place Along the road beneath the hill To finish by the barley-mill.