standard time, civil time civil time, local time based on universal time . Civil time may be formally defined as mean solar time plus 12 hr; the civil day begins at midnight, while the mean solar day begins at noon.
..... Click the link for more information. used within a given time zone. The earth is divided into 24 time zones, each of which is about 15° of longitude wide and corresponds to one hour of time. Within a zone all civil clocks are set to the same local solar time solar time, time defined by the position of the sun. The solar day is the time it takes for the sun to return to the same meridian in the sky. Local solar time is measured by a sundial .
..... Click the link for more information. . Adjacent zones typically differ by a whole hour, although there are instances, such as in Newfoundland and South Australia, of half-hour zones. Standard time is based on universal time universal time (UT), the international time standard common to every place in the world, it nominally reflects the mean solar time along the earth's prime meridian (renumbered to equate to civil time ).
..... Click the link for more information. . Standard time was largely the creation of the Canadian railway engineer Sir Sandford Fleming (1827–1915). Its establishment in the United States was mainly due to the efforts of the educator Charles Dowd and William Allen, secretary of the American Railroad Association. Standard time officially came into existence after a 19-nation White House meeting in 1884, with the prime meridian established at Greenwich, England. In the United States, time zones are regulated by the Dept. of Transportation.

See also daylight saving time daylight saving time (DST), time observed when clocks and other timepieces are set ahead so that the sun will rise and set later in the day as measured by civil time .
..... Click the link for more information. .

Bibliography

See C. Blaise, Time Lord: Sir Sandford Fleming and the Creation of Standard Time (2001).

standard time

Official local time of a region or country. Local mean solar time depends on longitude; it advances by four minutes per degree eastward. The Earth can thus be divided into 24 standard time zones, each approximately 15° in longitude. The actual boundaries of each time zone are determined by local authorities and in many places deviate considerably from 15°. The times in different zones usually differ by an integral number of hours; minutes and seconds are the same. See also Greenwich Mean Time.