Sixty-two second-, fourth-, and sixth-graders were asked to judge the temporal duration of objects and events when the objects were changed in height or subjected to decay, when an event was reversed, and when an event was given an affective dimension. Nonconservers of time were those who judged that these irrelevant transformations affected the temporal aspects of the objects or events. The shift from nonconservation to conservation of time occurred between the second and fourth grades for most problems. The results indicated that young (under eight or nine years) children's concept of time is surprisingly defective. The relation of these findings to other conservation concepts was discussed.