Benjamin Franklin suggested people set their clocks ahead in the summer as far back as 1784. The first systematic use of Daylight Saving Time did not occur until the Germans began setting clocks ahead in World War I to conserve fuel. Soon, Britian and other Western European countries had also adopted "Summer Time."
The U.S. observed this time change nationwide in 1918 and 1919 and again in World War II from February 9, 1942, through September 30, 1945.
War times have been the only periods that Daylight Saving Time has been observed uniformly in this nation. Local ordinance or state legislation has determined its recognition otherwise.
In 1921 the entire state of Oklahoma was included in the Central Standard Time Zone. After World War II, "Summer Time" was not observed in Oklahoma. From September 30, 1945, through 1967, Daylight Saving again was not observed. In 1966, Congress passed the Uniform Time Act requiring that any state or U.S. territory wishing to observe Daylight Saving Time had to begin and end it on the same dates the federal government used--2 a.m. the first Sunday in April through 2 a.m. the last Sunday in October. Any state that did not take legal action went on Daylight Saving Time automatically. Therefore, on April 30, 1967, Oklahoma went on Daylight Saving Time and has remained so for the federally designated time period each year.
Source: Action Line, Tulsa World, November 1, 1999.
Time Changes in the USA, 1966, by Doris Chase Doane.