<P> Congress then asked the National Bureau of Standards (NBS, today NIST) to evaluate the DOT report . Its report, "Review and Technical Evaluation of the DOT Daylight Saving Time Study" (April 1976), found no significant energy savings or differences in traffic fatalities . It did find statistically significant evidence of increased fatalities among school - age children in the mornings during the four - month period January--April 1974 as compared with the same period (non-DST) of 1973 . NBS stated that it was impossible to determine, what, if any, of this increase was due to DST . When this data was compared between 1973 and 1974 for the months of March and April, no significant difference was found in fatalities among school - age children in the mornings . </P> <P> In 1986 Congress enacted P.L. 99 - 359, amending the Uniform Time Act by changing the beginning of DST to the first Sunday in April and having the end remain the last Sunday in October . These start and end dates were in effect from 1987 to 2006 . The time was adjusted at 2: 00 a.m. local time . </P> <P> By the Energy Policy Act of 2005, daylight saving time (DST) was extended in the United States beginning in 2007 . As from that year, DST begins on the second Sunday of March and ends on the first Sunday of November . In years when April 1 falls on Monday through Wednesday, these changes result in a DST period that is five weeks longer; in all other years the DST period is instead four weeks longer . In 2008 daylight saving time ended at 2: 00 a.m. DST (0200) (1: 00 a.m. ST) on Sunday, November 2, and in 2009 it began at 2: 00 a.m. (3: 00 a.m. DST) on Sunday, March 8 . </P> <P> Under Section 110 of the Act, the U.S. Department of Energy was required to study the impact of the 2007 DST extension no later than nine months after the change took effect . The report, released in October 2008, reported a nationwide electricity savings of 0.03% for the year of 2007 . </P>

When did the daylight savings time rules change