I'd be reluctant to place that much weight on Kirk's attitude towards Klingons in a single other work...Was just thinking about this some more, and if we're looking at a revised timeline-placement for this novel, it would almost certainly have to occur prior to the events of In the Name of Honor, where Kirk's fundamental pre-TUC attitude towards the Klingons undergoes its final seismic shift, and where we first glimpse the near-bigoted attitude he holds early in that movie.
In Timetrap, Kirk still has not yet lost all of his goodwill towards the Klingons (despite the murder of his son, etc.), and during the course of the novel, is still willing to consider an outcome in which the Federation and the Klingon Empire can put aside their differences and work towards a common, beneficial future together. By the time period of Star Trek VI, all of that is now pretty much gone.
So...probably circa 2286, then, not long after the events of The Voyage Home, since Honor is officially the very "next" mission of the Enterprise-A following the Sybok incident, and with both stories (The Final Frontier and In the Name of Honor) taking place very early in 2287.
To offer a counterexample, there are plenty of DC Comics stories involving Kirk and Klingons which take place later than In the Name of Honour but don't feature such a strong antipathy on Kirk's part. I still prefer to "count" those stories, so Timetrap could just as easily fit in somewhere amongst them as it could beforehand.