In one embodiment, a method includes one or more server computing devices receiving first data associated with an activity recently performed or currently being performed by a user of one or more client computing devices. A current state of the user is inferred at least in part by analyzing at least the first data, and second data associated with one or more historical durations associated with the inferred current state is accessed. An end time associated with the inferred current state is estimated based at least in part on the second data.