I lost interest in this conversation when truth and fact began to get confused (I believe that's part of what Genkaus is trying to explain to you, that you're confusing truth (correspondence between assertion/belief and reality) and fact (the state of affairs itself)), but as for your question of when a fact changed: The fact of who the current president of the USA is, changes every few years, for example.
"The reason things will never get better is because people keep electing these rich cocksuckers who don't give a shit about you."
-George Carlin
-George Carlin