Most of the United States begins Daylight Saving Time (DST) 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.
In the U.S., 2:00 a.m. was originally chosen as the changeover time because it was practical and minimized disruption.
As per Webexhibits.org, 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.
Even though your brain knows that the time on the clock has changed, your body's internal clock does not. When the clocks move forward in the spring, you'll be robbed of an hour of sleep.
That night, you may not be able to fall into your normal sleep rhythms an hour earlier than you’re used to, and you won’t get as much quality sleep as you need. Check out some tips on how to deal with Daylight Saving Time at Sparkpeople.com.