The Uniform Time Act required a uniform method of observing DST in the U.S. While time change was not mandatory, any state that chose to participate in DST had to change the time during designated periods in the spring and fall.
The practice of setting clocks forward one hour in the spring and backward one hour in the fall, is a part of a program known in the U.S. as daylight time or daylight saving time (DST).
The U.S. Naval Observatory's Astronomical Applications Department: The USNO government site has an article with current DST information and the history of daylight time.
The California Energy Commission: The California Energy Commission provides information on the history of time change and the current DST schedule.
The automatic DST feature on these types of watches is convenient because you can avoid the hassle of manually changing the time.
The current time change schedule follows the Energy Policy Act of 2005, which extended DST to begin in March and end in November.
During the energy crisis of the 1970's, DST periods were temporarily extended several different times to save energy.
The results concluded that DST saves energy, helps prevent crime and cuts down on the number of traffic accidents.
A number of countries around the world such as the U.S., Canada, U.K., Chile and Russia observe some form of DST.
For the 2 polygon has a right angle at a=a, a', and a zero angle at u = b, where 0 changes from o to 27/n and 1 - 2 increases by 21-rr/n; so that dSt A (b -a.b -a') a - (u -b),/ (u - a.u - a where A= tn (II) And the w polygon has a zero angle at u =o, oo, where 4, changes from o to m and back again, so that w changes by im, and du =B, where B=-.