Sometimes while sending armies out, they don't return on time.  I think something happens when they turn around and their travel time is established for the return leg of the journey.  This can become a bit of an issue during an active conflict- when you need to dodge armies, and in my case, when you need your defenders to return home right after a large siege train rips the city apart, leading to a potential raze attempt that you wish to defend against.

In the specific case that I just had today, the army had been sent on a 9.5 hour march, and the intention was for it to turn around and march another 9.5 hours to get home, for a total of 19 hours.  Instead, they are now taking 17 hours for the march back, for a total journey of about 26.5 hours.  

I used the "feint" option, but I don't think that is relevant.  I included troop types in my petition, but I doubt that is important either.  What might be relevant is the use of gear that affects travel times in elite divisions.

I could see the travel time changing after a combat that affects the army composition, but fail to see how or why it would change when no combat has taken place.

At this point, I'm calling this a bug.  Has anyone else had similar experiences?