A 1996 change in shopping hours regulations in the Netherlands provides an opportunity to study the effects of timing constraints on total time spent in shopping, working, and other activities as well as the timing of these activities. We develop a simple structural model to make predictions about the effects of imposition and relaxation of a timing constraint on time use patterns, and utilize time diary data from 1995, 1997, 1999, and 2000 to examine time use patterns by demographic group before and after the change. In addition to a change in the timing of shopping, we find a non-negligible increase in the total time spent shopping.