Daylight saving time

[Dave Monroe]

Starting in 2007, daylight time begins in the United States on the
second Sunday in March and ends on the first Sunday in November. On
the second Sunday in March, clocks are set ahead one hour at 2:00 a.m.
local standard time, which becomes 3:00 a.m. local daylight time. On
the first Sunday in November, clocks are set back one hour at 2:00
a.m. local daylight time, which becomes 1:00 a.m. local standard time.
These dates were established by Congress in the Energy Policy Act of
2005, Pub. L. no. 109-58, 119 Stat 594 (2005).

Not all places in the U.S. observe daylight time. In particular,
Hawaii and most of Arizona do not use it. Indiana adopted its use
beginning in 2006.

http://aa.usno.navy.mil/faq/docs/daylight_time.php

Most of the United States begins Daylight Saving Time at 2:00 a.m. on
the second Sunday in March and reverts to standard time on the first
Sunday in November. In the U.S., each time zone switches at a
different time.

[...]

During DST, clocks are turned forward an hour, effectively moving an
hour of daylight from the morning to the evening.

http://www.webexhibits.org/daylightsaving/b2.html

Daylight saving time

http://en.wikipedia.org/wiki/Daylight_saving_time