Does mere passage of time have causal powers ?  Are properties like "being n days past" causally efficient ?  A pervasive intuition among metaphysicians seems to be that they don't.  Events and/or objects change, and they cause or are caused by other events and/or objects; but one does not see how just the mere passage of time could cause any difference in the world. 
In this paper, I shall discuss a case where it seems that mere passage of time does have causal powers : Sydney Shoemaker's (1969) possible world where temporal vacua (allegedly) take place.  I shall argue that Shoemaker's thought-experiment doesn't really aim at teaching us that there can be time without change, but rather that if such a scenario is plausible at all (as I think it is) it provides us with good reasons to think that mere passage of time can be directly causally efficient.