I was talking about this with my history teacher today. Surely, periods of hundreds of years, such as the renaissance or the world war eras, aren't recognized as these until much later. As for the middle ages, when did people realize that society was staying pretty much the same for extended periods of time, and what jumpstarted the cultural revolution known today as the renaissance?
Hello! I think it's important to point out that the idea of the early medieval period as a "dark age" has actually been rejected by most historians. Here is the relevant thread:
http://www.reddit.com/r/AskHistorians/comments/235w3l/why_are_the_european_dark_ages_considered_a/