standard timestandard time
- the time in any of the 24 time zones, each an hour apart, into which the earth is divided: it is based on distance east or west of Greenwich, England; the 8 zones of North America (Atlantic, Eastern, Central, Mountain, Pacific, Alaska, Hawaii-Aleutian, and Samoa) use the mean solar times of the 60th, 75th, 90th, 105th, 120th, 135th, 150th, and 165th meridians, respectively
- the official time, whether mean solar time or daylight saving time, in any given region
The time in any of 24 time zones, usually the mean solar time at the central meridian of each zone. In the continental United States, there are four standard time zones: Eastern, using the 75th meridian; Central, using the 90th meridian; Mountain, using the 105th meridian; and Pacific, using the 120th meridian.