when did the usa start using daylight savings time
History of time in the United States During World War II, Congress enacted the War Time Act (56 Stat. 9) on January 20, 1942. Year-round DST was reinstated in the United States on February 9, 1942, again as a wartime measure to conserve energy resources.[5] This remained in effect until after the end of the war. The Amendment to the War Time Act (59 Stat. 537), enacted September 25, 1945, ended DST as of September 30, 1945. During this period, the official designation War Time was used for year-round DST. For example, Eastern War Time (EWT) would be the equivalent of Eastern Daylight Time during this period.