Life as we know it on Earth exists between approximately −15°C and 120°C, a narrow sliver of the range of temperatures found throughout the universe. Because of the strong temperature sensitivity of most biochemical reactions, it comes as no surprise that even small temperature variations within these limits, such as those associated with gradual climate change, have profound effects on living organisms. It is also easy to see the adaptive significance of evolved mechanisms that allow organisms to anticipate changes in environmental temperature and adjust to them. Many animals exhibit differential activity patterns in warmer versus colder seasons, hibernation being an extreme example. Seasonal timekeeping mechanisms that govern these behaviors often make use of day length as a reliable indicator of the time of year. In this context, day length is commonly measured by the coincidence of light and certain phases of the internal daily time keeping mechanisms of the circadian clock (Dunlap et al., 2004).