The following is an article for February 9, 1942 at History.com
On this day, Congress pushes ahead standard time for the United States by one hour in each time zone, imposing daylight saving time–called at the time “war time.”
Daylight saving time, suggested by President Roosevelt, was imposed to conserve fuel, and could be traced back to World War I, when Congress imposed one standard time on the United States to enable the country to better utilize resources, following the European model. The 1918 Standard Time Act was meant to be in effect for only seven months of the year–and was discontinued nationally after the war. But individual states continued to turn clocks ahead one hour in spring and back one hour in fall. The World War II legislation imposed daylight saving time for the entire nation for the entire year. It was repealed Sept. 30, 1945, when individual states once again imposed their own “standard” time. It was not until 1966 that Congress passed legislation setting a standard time that permanently superceded local habits.