The Answer: The first national observance of Daylight Saving Time in the United States was in 1918, to save energy during World War I. This lasted seven months before being repealed.A similar, year-round, national observance went into effect in World War II, starting February 9, 1942, and ending September 30, 1945.he Answer: The first national observance of Daylight Saving Time in the United States was in 1918, to save energy during World War I. This lasted seven months before being repealed.