(1) I was taught that everything that happens is "historical." That is, it is part of history.
(2) "Historic" is used to refer to something VERY SPECIAL in history.
(3) I live in a big city.
(a) Some of the buildings are very old.
(i) Since the United States is "younger" than most other countries, "old" sometimes means only 100 or 200 years old.
(a) Some houses in my city are protected as "historic buildings." They may not be demolished (destroyed). Maybe a famous person once lived there; maybe it has an architecture that is no longer used; etc.
(b) If you visit Washington D. C., you will want to visit Mount Vernon. That is the house where President George Washington lived. It is historic. Of course, no one may demolish it.
(c) When you think of New York City, what historic monument do you immediately think of? The historic Statue of Liberty. Right?
(4) Dates are often historic.
(a) This is a language website, so we do not discuss politics. But I think that I am permitted to say that 1989 was a historic year in the history of Europe. I am sure that you know about the events that happened in 1989.
(b) And everybody agrees that the 2008 presidential election in the United States was historic. Something happened that had never happened before in the history of the United States.