| the civil time officially adopted for a country or region, usually the civil time of some specific meridian lying within the region. The standard time zones in the U.S. (Atlantic time, Eastern time, Central time, Mountain time, Pacific time, Yukon time, Alaska-Hawaii time, and Bering time) use the civil times of the 60th, 75th, 90th, 105th, 120th, 135th, 150th, and 165th meridians respectively, the difference of time between one zone and the next being exactly one hour. |
| standard time n. 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. |