Daylight Saving Time (DST) is the practice of turning the clock ahead as warmer weather approaches and back as it becomes colder again so that people will have one more hour of daylight in the afternoon and evening during the warmer season of the year. (Some believe that it should be called Daylight Shifting Time because no daylight is actually "saved.") Daylight Saving Time varies somewhat from country to country. Countries in equatorial and tropical climates do not observe Daylight Saving Time. The months when the clock is set ahead and back differ between northern and southern hemispheres.