Consider **watershed**: > an event or time when important changes happen in history or in your > life ([Longman][1]) Example: > The 1932 election represented a **watershed** in American politics. If a phrase is OK, **critical juncture** might work. > juncture: a point of time, esp. one made critical by a concurrence of > circumstances (http://www.thefreedictionary.com/juncture) Example: > The 1930s was **a crucial time of change** in Latin America, a **"critical > juncture"** in David Collier's and Ruth Berins Collier's terms. (source on [Google Books][2]) [1]: http://www.ldoceonline.com/dictionary/watershed [2]: https://books.google.com/books?id=mBWiXGzBTN8C&pg=PA287&lpg=PA287&dq=%22The%201930s%20was%20a%20crucial%20time%20of%20change%20in%20Latin%20America,%20a%20critical%20juncture%22&source=bl&ots=ouskTFgjfB&sig=g_uWMs-2gZhU36oistJS3oyZd8Q&hl=en&sa=X&redir_esc=y#v=onepage&q&f=false