 Preferences relate to time in several ways. Preference at one point in time can refer to what happens or happened at other points in time. Furthermore, preferences can change over time, due to changes in beliefs, values, tastes, or a combination of these. Section 7.1 explains why preference change requires explanatory and theoretical  treatment. In the following sections, three types of explanatory models are discussed. (For more detail, see Grüne-Yanoff and Hansson 2009.)  Time preference models (section 7.2) only refer to the temporal relationship between the occurrence of a preference and the objects it refers to. Doxastic change models (section 7.3) investigate how a change of an agent’s beliefs leads to a change in her preferences. Valuational change models (section 7.4) investigate how a change in an agent’s basic evaluations leads to a change in her preferences.