Yesterday I was asked at work what the origins of daylight savings were. People who know me know I can never just say "I don't know" to a question like that—I had to go do some research.
The short answer is "war and golf" but here is a longer version, gleaned from various articles online and a little prior knowledge on the topic.
While Benjamin Franklin is sometimes credited with the idea of setting clocks differently in the summer, his idea was well before its time as there wasn't a notion of standard time in his day. The notion that clocks would be set according to the "real time" (i.e. based on the Sun) of some other location has its origin with the railroad system. In November 1840, the Great Western Railway in England adopted London Time for all their schedules. The US and Canada followed suit with their own Standard Time in November 1883.
While Standard Time was initially for the railroads, it began to be adopted across the board, eventually being enacted into law in the US by the Standard Time Act of 1918.
An Englishman, William Willet made the observation, a century after Ben Franklin had done the same, that people were wasting the early hours of the day in summer by sleeping in. He was also an avid golfer who was frustrated at dusk cutting short his game. So he started campaigning for clocks to be advanced during the summer months. The idea was ridiculed and he died in 1915 without seeing his idea adopted.
In April 1916, however, Germany started advancing the clock an hour to reduce electricity usage and hence fuel consumption during the war. Many European countries immediately followed suit and Britain started in May 1916. When the US joined the war, they too adopted this daylight saving measure.
US Congress repealed the law in 1919, but Woodrow Wilson (incidentally also an avid golfer) vetoed the repeal. Congress overrode the veto and so daylight saving stopped, although was adopted locally in some places.
In World War II, it was reintroduced, this time all year around. The US had daylight saving from February 1942 to September 1945. After the war, it went back to being a local issue.
It was a controversial issue through the early 1960s but the confusion caused by so many local differences resulted in the US passing the Universal Time Act in 1966 which reintroduced it across the country unless overridden by state law.
My own home state of Western Australia is currently in a three-year trial of daylight saving and will hold a vote next year as to whether to keep it.