2am March 31, 1918.
Currently, daylight saving time starts on the second Sunday in March and ends on the first Sunday in November, with the time changes taking place at 2:00 a.m. local time. Most areas of the United States currently observe daylight saving time (DST), the exceptions being Arizona (except for the Navajo Nation, which does observe daylight saving time), Hawaii, and the overseas territories of American Samoa, Guam, the Northern Mariana Islands, Puerto Rico and the United States Virgin Islands. Facts: Sunday, November 1, 2015 - Daylight Saving Time ends at 2am. Set clocks back one hour. Sunday, March 13, 2016 - Daylight Saving Time begins at 2am. Set clocks ahead one hour. It is Daylight Saving Time (singular), not Daylight Savings Time (plural). Beginning in 2007, Daylight Saving Time starts in the United States on the second Sunday in March and ends on the first Sunday in November.  Beginning in 2007: Daylight Saving Time begins at 2 a.m. on the second Sunday of March Daylight Saving Time ends at 2 a.m. on the first Sunday of November. The corresponding time zones in Canada also switch to Daylight Saving Time on the same dates. Daylight Saving Time begins at 2 a.m. on the first Sunday of April Daylight Saving Time ends at 2 a.m. on the last Sunday of October. Daylight Saving Time begins at 2 a.m. on the second Sunday of March Daylight Saving Time ends at 2 a.m. on the first Sunday of November. Daylight Saving Time begins at 2 a.m. on the first Sunday of April Daylight Saving Time ends at 2 a.m. on the last Sunday of October. The Federal law was amended in 1986 to begin Daylight Saving Time on the first Sunday in April. Under legislation enacted in 1986, Daylight Saving Time in the U.S. began at 2:00 a.m. on the first Sunday of April and ended at 2:00 a.m. on the last Sunday of October. ' An Act to preserve daylight and provide standard time for the United States ' was enacted on March 19, 1918. [See law] It both established standard time zones and set summer DST to begin on March 31, 1918. Daylight Saving Time was observed for seven months in 1918 and 1919. Under legislation enacted in 1986, Daylight Saving Time in the U.S. began at 2:00 a.m. on the first Sunday of April and ended at 2:00 a.m. on the last Sunday of October. Daylight Saving Time in Canada. In most of Canada Daylight Saving Time begins at 2:00 a.m. local time on the second Sunday in March. On the first Sunday in November areas on Daylight Saving Time return to Standard Time at 2:00 a.m. local time. When Daylight Saving Time begins turn your clocks ahead one hour.  As of 2007, daylight time begins in the United States on the second Sunday in March and ends on the first Sunday in November. On the second Sunday in March, clocks are set ahead one hour at 2:00 a.m. local standard time (which becomes 3:00 a.m. local daylight time). On the first Sunday in November, clocks are set back one hour at 2:00 a.m. local daylight time (which becomes 1:00 a.m. local standard time). Beginning in 2007, daylight time starts on the second Sunday in March and ends on the first Sunday in November. For a very readable account of the history of standard and daylight time in the U.S., see. Ian R. Bartky and Elizabeth Harrison: Standard and Daylight-saving Time, , May 1979 (Vol. 240, No. 5), pp. 46-53.
https://en.wikipedia.org/wiki/Daylight_saving_time_in_the_United_States http://www.cnn.com/2013/08/22/world/daylight-saving-time-fast-facts/index.html http://eclipse.gsfc.nasa.gov/SEhelp/daylightsaving.html http://eclipse.gsfc.nasa.gov/SEhelp/daylightsaving.html http://www.webexhibits.org/daylightsaving/e.html http://www.webexhibits.org/daylightsaving/e.html http://www.timetemperature.com/canada/daylight_saving_time_canada.shtml http://aa.usno.navy.mil/faq/docs/daylight_time.php
when did daylight savings time begin