Daylight saving time in the United States is the practice of setting the clock forward by one hour during the warmer part of the year, so that evenings have more daylight and mornings have less. Most areas of the United States currently observe daylight saving time (DST), the exceptions being Arizona (except for the Navajo Nation, which does observe daylight saving time), Hawaii, and the overseas territories of American Samoa, Guam, the Northern Mariana Islands, Puerto Rico and the United States Virgin Islands.