The history of standard time in the United States began November 18, 1883, when United States and Canadian railroads instituted standard time in time zones. Before then, time of day was a local matter, and most cities and towns used some form of local solar time, maintained by some well-known clock (for example, on a church steeple or in a jeweler’s window). The new standard time system was not immediately embraced by all.
Use of standard time gradually increased because of its obvious practical advantages for communication and travel. Standard time in time zones was not established in US law until the Standard Time Act of 1918 of March 19, 1918, also known as the Calder Act (15 USC 260). The act also established daylight saving time, itself a contentious idea.
Daylight saving time was repealed in 1919, but standard time in time zones remained in law, with the Interstate Commerce Commission (ICC) having the authority over time zone boundaries. Daylight time became a local matter. It was re-established nationally early in World War II, and was continuously observed until the end of the war.
After the war its use varied among states and localities. The Uniform Time Act of 1966 provided standardization in the dates of beginning and end of daylight time in the U.S. but allowed for local exemptions from its observance. The act also continued the authority of the ICC over time zone boundaries. In subsequent years, the United States Congress transferred the authority over time zones to the U.S. Department of Transportation (DOT), modified (several times) the beginning date of daylight time, and renamed the three westernmost time zones.
Time zone boundaries have changed greatly since their original introduction and changes still occasionally occur. DOT issues press releases when these changes are made. Generally, time zone boundaries have tended to shift westward. Places on the eastern edge of a time zone can effectively move sunset an hour later (by the clock) by shifting to the time zone immediately to their east.
If they do so, the boundary of that zone is locally shifted to the west; the accumulation of such changes results in the long-term westward trend. The process is not inexorable, however, since the late sunrises experienced by such places during the winter may be regarded as too undesirable. Furthermore, under the law, the principal standard for deciding on a time zone change is the “convenience of commerce”. Proposed time zone changes have been both approved and rejected based on this criterion, although most such proposals have been accepted.
Starting March 11, 2007, DST was extended another four to five weeks, from the second Sunday of March to the first Sunday of November. The change was introduced by Representatives Fred Upton (R-MI) and Edward Markey (D-MA) and added to the Energy Policy Act of 2005; the House had originally approved a motion that would have extended DST even farther from the first Sunday in March to the last Sunday in November, but Senators Jeff Bingaman (D-NM) and Pete Domenici (R-NM) agreed to scale back the proposal in conference committee due to complaints from farmers and the airline industry. Proponents claimed that the extension would save “the equivalent of” 10,000 barrels (1,600 m3) of oil per day, but this figure was based on U.S. Department of Energy information from the 1970s, the accuracy and relevance of which the DoE no longer stands by. More recent studies by the Department of Energy and California Energy Commission have predicted much smaller energy benefits. There is very little recent research on what the actual positive effects, if any, might be.
Since DST moves sunrise one hour later by the clock, late sunrise times become a problem when DST is observed either too far before the vernal equinox or too far after the autumnal equinox. Because of this, the extension was greeted with criticism by those concerned for the safety of children who would have been forced to travel to school before sunrise, especially in the month of March. In addition, the airline industry was especially concerned if DST were to be extended through to the last Sunday in November, as this is very often (6 out of every 7 years) the Sunday after Thanksgiving. This is one of the busiest travel days at American airports, and could have resulted in much havoc among travelers who forgot that the clocks were changing that day.