The current logic is to use the phrase "just now" for [time intervals less than four seconds](http://meta.stackoverflow.com/questions/104921/bug-in-comment-timestamp/104939#104939) in duration.  

If it isn't too much trouble to implement, I think the user should just be allowed to accept the answer (the error message is *not* displayed) if the timer is within five seconds of expiring anyway.

Extra points for doing it this way on any timer that inhibits an action.