According to the Dux bed people, who apparently take of a very Leibnizian perspective on things, everything! I was listening to their ad on the radio this morning. The woman doing the pitch was talking about her grandmother having owned a Dux bed for 56 years now. "What was happening in 1952?" she asked. "Well, Alaska would not become a state for another seven years."
This presumably "happened" continually throughout the year, as the date of statehood became closer and closer. And, of course, the fall of the Roman Empire happened in 1952 as well, in terms of its date becoming more distant.
And so did every other event, past or future, all also happen in 1952. And every other year. History books are going to get really big. Or small, I'm not sure which.