Benjamin Franklin is credited with the concept of Daylight Saving Time. The basic idea is to make the best use of daylight hours by shifting the clock forward in the Spring and backward in the Fall. Daylight Saving Time has been in use throughout much of the United States, Canada and Europe since World War I. In 1966, President Lyndon Johnson signed an act into law whereby Daylight Saving Time begins on the last Sunday of April and ends on the last Sunday of October each year. However, any State can opt out of Daylight Saving Time by passing a State law.