... Oversight of DST first resided with the Interstate Commerce Commission. In 1966, the U.S. Congress transferred that responsibility to the newly created Department of Transportation. Congress ordered the agency to "foster and promote widespread and uniform adoption and observance of the same standard of time within and throughout each such standard time zone."

So why is a transportation authority in charge of time laws? Bill Mosley, a public affairs officer at the U.S. Department of Transportation, explains that it all dates back to the heyday of railroads.

"In the early 19th century … localities set their own time," Mosley said. "It was kind of a crazy quilt of time, time zones, and time usage. When the railroads came in, that necessitated more standardization of time so that railroad schedules could be published."

In 1883 the U.S. railroad industry established official time zones with a set standard time within each zone. Congress eventually came on board, signing the railroad time zone system into law in 1918.

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 That section of the act was repealed the following year, and DST thereafter became a matter left up to local jurisdictions.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. ...