This is from an article in Wired about solar eclipses in the distant past:
Nice, eh? A niggling point is that they did not, or were not the first, to coin the word. (Google: 3,740 hits). But the term has what appear to be multiple slightly different usages. The Double-Tongued Dictionary provides this cite:
Using the same calculating methods that predict future eclipses, astronomers have been able to calculate when eclipses occurred in the past. You can run the planetary clock in reverse as well as forward. To coin a word, you can postdict as well as predict.
Approximately one in five suspect identifications from sequential lineups may be wrong. As a result, no existing eyewitness identification procedure can relieve the courts of the burden of decide after the fact (or postdicting) which eyewitness identifications are accurate versus inaccurate.This sense seems relatively established in the literature of psychology, where its sibling term postdictor is flung about with abandon.
Postdiction is also used in a dismissive sense to refer to "prediction after the fact" by people who are skeptical of, you know, prophecies. Think Nostradamus.
For the general idea of running the clock backward, as the Wired article puts it, there is also the term retrodiction. As defined in Wikiepdia, retrodiction is a way to test theories by comparing against past results in situations when comparing against future ones is impractical. You see this in economics, when economic models are tested by running them against data from the past to see if your model can, for example, accurately predict the mortgage crisis. Some might say that this constitutes that other, more dismissive sense of postdiction, but hey.
As an interesting aside, the very next paragaph in the Wired article has this bold usage:
The most likely candidate for Thales' eclipse took place on May 28, 585 B.C., though some authorities believe it may have been 25 years earlier in 610 B.C. Hundreds of scholars have debated this for nearly two millenniums.This invites a discussion of forming plurals for terms that immigrated from non-English sources. I have an opinion on that, actually, which you can read here.