The time in any of the twenty-four time zones, each an hour apart, into which the earth is divided. It is based on distance east or west of Greenwich, England. The eight zones of North America, Atlantic, Eastern, Central, Mountain, Pacific, Alaska, Hawaii-Aleutian, and Samoa Standard Times, use the mean solar times of the 60th, 75th, 90th, 105th, 120th, 135th, 150th, and 165th meridians, respectively.