Most U.S. residents set their clocks one hour forward in spring and one hour back in fall. However, residents of Arizona and Hawaii—along with the U.S. territories of Puerto Rico and the Virgin Islands, among others—will do nothing. Those locales never deviated from standard time within their particular time zones.

Contrary to popular belief, no federal rule mandates that states or territories observe daylight saving time.

Federal law simply stipulates that areas that do switch back to standard time at 2 a.m. on the last Sunday in October.

Likewise, the rule requires that regions that observe daylight saving time, or DST, begin the period at the same time on the first Sunday in April.

This is the last year, however, in which daylight saving