I believe the easiest way to logically represent what you are saying is:
(P → ~S) → (F → ~S)
That is, if something is false in the past, it will be false in the future. This assumes that the fact expressly or implicitly specifies the temporal conditions under which it is supposed to be true, thus making its truth value timeless.
The same thing can be represented in predicate logic to express it for any fact whatsoever:
∀x[(P → ~Sx) → (F → ~Sx)]
The negation of this proposition doesn't imply any contradictions, but it does imply conclusions that most people would consider absurd. The following immediately follows from denying it:
Ǝx[F & Sx & (P → ~Sx)]
That might be translated as:
There exists at least one future fact, which was false in the past.
If we consider that propositions are true in virtue of them being consistent with reality, the possibility of the truth value of facts changing could only mean the possibility of reality itself changing. Therefore, the denial of your proposition implies that history would not be fixed, and the following could be the case: Today, it is true that George Washington was the first president of the United States, but ten years from now that might be untrue — not because someone rewrote history but because reality itself for that period somehow underwent a change.
The denial of your proposition would also imply uncertainty with respect to everything. If one of the facts of one event could change, then who's to say that every fact couldn't also change? If reality were in a constant flux, it would be impossible to know anything at all.