The Collaborative International Dictionary of English v.0.48:

Postfact \Post"fact`\, a. [See Post-, and Fact.]
   Relating to a fact that occurs after another.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Postfact \Post"fact`\, n.
   A fact that occurs after another. "Confirmed upon the
   postfact." --Fuller.
   [1913 Webster]