Ben Franklin was actually the first to suggest the concept. Franklin wrote of being awakened at 6 a.m. while serving as an ambassador to France, and of being surprised to note that the sun rose much earlier than he normally did. He realized that enormous amounts of resources would be saved if he and his companions rose before noon, and by doing so burned less midnight oil. He then wrote to a newspaper of his idea. So, he was the first to understand that daylight should be taken advantage of; however, he did not really know what to do with his realization.
Daylight savings were recognized in a more major way during World War I. Germany was the first state to implement the time changes, as a means of reducing artificial lighting to save coal for the war. The practice was soon adopted by many.
In 1918 the U.S. federal law set the start and end of daylight saving time for the states that chose to follow it. In World War II, however, daylight savings became mandatory for the whole country, also as a way to save war resources. After the war ended, daylight savings became optional once again.