Yes it is
Tactics Trainer
http://support.chess.com/Knowledgebase/Article/View/53/0/how-does-time-affect-my-tactics-rating
Note that from Tactics Settings, you can turn ON a visible timer (most people find it distracting) and you can also opt for unrated tactics to remove the time element (probably not as instructive in the long run).
Merry Christmas all!
Just a quick question about the Tactics Trainer..
Sometimes after completing a challenge it subtracts rating points. Is that a normal feature of the Tactics Trainer? Perhaps taking too long trying to find the solution?
Great site by the way, loving the Chess Mentor.