The only federal regulatory agency in existence at that time happened to be the Interstate Commerce Commission, so Congress granted the agency authority over time zones and any future modifications that might be necessary.
Part of the Act of 1918 also legislated for the observance of daylight saving time nationwide. That section of the act was repealed the following year, and DST thereafter became a matter left up to local jurisdictions.
Daylight saving time was observed nationally again during World War II, but was not uniformly practiced after the war's end.
Finally, in 1966, Congress passed the Uniform Time Act, which standardized the start and end dates for daylight saving time but allowed individual states to remain on standard time if their legislatures allowed it.
A 1972 amendment extended the option not to observe DST to areas lying in separate time zones but contained within the same state.
Before the move by Congress last year to extend DST, the most recent modification occurred in 1986, when the start date was moved from the last Sunday in April to the first Sunday in April.
According to Mosley, the drive behind the switch is "to adjust daylight hours to when most people are awake and about."
Daylight saving time decreases the amount of daylight in the morning hours so that more daylight is available during the evening.
Not everyone benefits from the change, Mosley conceded. Farmers and others who rise before dawn may have to operate in the dark a while longer before daybreak.
Daylight saving time, however, can bring many benefits. Mosley said research has shown that more available daylight increases energy savings while decreasing the number of traffic accidents, traffic fatalities, and incidences of crime.
Congress noted other advantages while updating legislation in 1986, including "more daylight outdoor playtime for the children and youth of our Nation, greater utilization of parks and recreation areas, expanded economic opportunity through extension of daylight hours to peak shopping hours and through extension of domestic office hours to periods of greater overlap with the European Economic Community."
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