One source of yearly starting and ending dates of daylight savings time through 2025 is the website for the U.S. Naval Observatory's Astronomical Applications Department, as of 2015. Daylight Savings Time begins on the second Sunday of each March and ends on the first Sunday of each November.
Clocks are set forward one hour at 2 a.m. on the first day of Daylight Savings Time and back one hour at 2 a.m. on the last day, as in the popular mnemonic device "spring ahead, fall back." The United States Department of Transportation regulates and oversees Daylight Savings Time.
Dates for the beginning and end of Daylight Savings Time were not standardized nationally until 1966, and it has never been obligatory for all parts of the United States to observe the seasonal time change at all. Hawaii and most of Arizona do not.