Wasn't it Germany who implemented it in the early 20th century? I think the railroads came up with the idea here in North America to keep trains on schedule. I take it you don't travel much.
The history of DST is quite a mess. It is right that Germany implemented DST in 1916, in hopes to save some valuable ressources for the war effort, quickly followed by France and Britain. But the Weimar Republic ended this unloved war measure again in 1919, while Britain kept it going between the wars. In 1940, during WWII, DST made a return in german territories, for the same reason as in WWI. After the war, there were experiments with double DST and such, but in 1949, DST was ended once more in both Germanies.
At that time, DST was slowly fading out in Europe. The oil crisis in 1973 started considerations in Europe to revisit DST, but only France would actually implement it in 1976. In an uncoordinated attempt to get the resulting issues with trade and travel solved, many other west european countries followed suit, except West Germany, wich hesitatde because they didnt want to raise the iron curtain by adding a time difference to the mix. When the GDR announced in 1979 for the following year to implement DST, FRG quickly followed suit. Many other european states that had heasitated until then, now jumped onto the bandwagon, with Switzrland being the last joining in 1981. It took until 1996 to get all countries of the EU to harmonize their DST to a common date and time, which starts ever since on the last sunday in March, at 2 AM and ends on the last sunday of October, at 3 AM.
The US first implemented DST first in WWi until its end. WWII saw the States applying a war time, which was like DST, but for the entire year. Outside of these times, DST was regionally or even locally used, which sometimes divided cities into several time zones. It wasn't before 1966 that a federal law determined when DST would start and end. The Energy Policy Act of 2005 changed these times from 2007 on to the times you are familiar to now. Though this still isn't a synchronized effort, as some states (Arizona, Hawaii) don't have DST and the others set their clocks according to the time zone they are in.