If everything is historic, then nothing is historic, just historical - Out of the ordinary events are not all historic events

We have historic elections; historic price movements; and historic political battles. The list can go on. The term historic is overused and thus loses meaning. Events can be out of ordinary but not historic. All market surprises are not historic. If everything is historic, then nothing is historic just historical. 

We cannot know what is historic in real time although the definition of historic includes what is "potentially famous or important in history."  We really need the passage of time to determine whether an event is historic.

Any commentary that says some event is historic is a good reason to fade. The historic will be a memory tomorrow and should be viewed as potential drivers of over-reaction. Quantitative analysis is a rational response to the emotions of using words like historic. A frequentist would compare similar events that can be counted to form a measure of extraordinary. The Bayesian would build a prior and then judge the relevance of new information. All "historic" events should be placed in context with other past events to determine whether it is meaningful. If there is not context, there is no meaning. For example, being the first at anything is special and emotional for the winner and his followers. It may create fame and it may be worth noting but it may not change the environment or structure of the world we live in. At least we cannot provide an immediate answer.  

Historic is often tied to emotions. A dispassionate commentator is less likely to use the term historic. The deep study of memory and emotions tells us that what we may view today as important in the future will not be once arrive in the future. Emotional state swill change over time. According to Elizabeth Kensinger, memories are both "resolute and fragile".

Daniel Kahneman focused much of his later study on "predictive utility" or as others refer to as "affective forecasting". What people predict will give them happiness or pain will change through time. Similarly, what we predict today will be historic will change. In general, historic events today will be just history tomorrow.