EPOCH

[noun] [C] [plural] epochs [formal or literary] - a long period of time, esp. one in which there are new advances and great changeThe president said that his country was moving into a new epoch which would be one of lasting peace.An event might be described as epoch-making if it has a great effect on the future.The landing on the moon was regarded as epoch-making/an epoch-making event but somehow failed to be as significant as was expected.