Daylight Saving Time ends Sunday, Nov. 4 at 2 a.m.
Be sure to "fall back" and set your clocks accordingly. Many electronic devices automatically adjust when Daylight Saving Time begins or ends. It begins again on March 10, 2013.
In the U.S., 2 a.m. was originally chosen as the changeover time because it was practical and minimized disruption. Most people were at home and this was the time when the fewest trains were running. It is late enough to minimally affect bars and restaurants, and it prevents the day from switching to yesterday, which would be confusing. It is early enough that the entire continental U.S. switches by daybreak, and the changeover occurs before most early shift workers and early churchgoers are affected.
Arizona, Puerto Rico, Hawaii, U.S. Virgin Islands and American Samoa do not observe Daylight Saving Time. Around the world, about 75 countries and territories have at least one location that observes DST, according to TimeandDate.com. However, 164 countries don't observe the time change at all.