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.
This entry comes from Encyclopædia Britannica Concise.
For the full entry on standard time, visit Britannica.com.
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