standard time

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Time as measured by synchronizing clocks in different geographical locations within a time zone to the same time, rather than using the local meridian, as in local mean time or solar time.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the official time in a local region (adjusted for location around the Earth); established by law or custom