Falling back

National Geographic has an article about Daylight Savings Time:

Daylight saving time in most of the United States ends at 2 a.m. local time on Sunday, 1 November. Contrary to popular belief, no federal rule mandates that U.S. states or territories observe daylight saving time. Most U.S. residents set their clocks one hour forward in spring and one hour back in fall. But people in Hawaii and most of Arizona, along with the U.S. territories of Puerto Rico, American Samoa, and the Virgin Islands, will do nothing. Those locales never deviate from standard time within their particular time zones.
The federal law first passed in 1918 and, thanks to a 2005 revision that went into practice in 2007, now stipulates areas that observe daylight saving time must switch back to standard time at 2 a.m. on the first Sunday in November.
Likewise, the new daylight saving time rule requires that regions that observe daylight saving time begin at the same time on the second Sunday in March.

Rico says there's a lot more at the site.