<P> During World War I , in an effort to conserve fuel , Germany began observing DST on May 1 , 1916 . The rest of Europe soon followed . The plan was not adopted in the United States until the Standard Time Act of March 19 , 1918 , which confirmed the existing standard time zone system and set summer DST to begin on March 31 , 1918 ( reverting October 27 ) . The idea was unpopular and Congress abolished DST after the war , overriding President Woodrow Wilson 's veto . DST became a local option and was observed in some states until World War II , when President Franklin Roosevelt instituted year - round DST , called `` War Time '' , on February 9 , 1942 . It lasted until the last Sunday ( the 30th ) in September 1945 . After 1945 many states and cities east of the Mississippi River ( and mostly north of the Ohio and Potomac rivers ) adopted summer DST . </P>
when did day light savings start in the us
March 31 , 1918