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(September 2012)| A time zone is a region on Earth that has a
uniform standard time for legal, commercial, and social
purposes. It is convenient for areas in close commercial or
other communication to keep the same time, so time zones tend to
follow the boundaries of countries and their subdivisions. Most
of the time zones on land are offset from Coordinated Universal
Time (UTC) by a whole number of hours (UTC−12 to UTC+14), but a
few are offset by 30 or 45 minutes. Some higher latitude
countries use daylight saving time for part of the year,
typically by changing clocks by an hour. Many land time zones
are skewed toward the west of the corresponding nautical time
zones. This also creates a permanent daylight saving time
effect. Early timekeeping  Before the invention of clocks,
people marked the time of day with apparent solar time (also
called "true" solar time) – for example, the time on a sundial –
which was typically different for every settleme