greenw.txt - ¿¿¿ Eastern European Summer Time UTC 3 ...

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Eastern European Summer Time (UTC+3)
Moscow Time / Turkey Time (UTC+3)
pale colours indicate where standard time is observed all year; dark colours
indicate where a summer time is observed
Time zones of Africa:
-01:00 Cape Verde Time[a]
±00:00 Greenwich Mean Time
+01:00
Central European TimeWest Africa Time
+02:00
Central Africa TimeEastern European TimeEgypt Standard TimeSouth African Standard
Time
+03:00 East Africa Time
+04:00
Mauritius Time[b]Seychelles Time[b]
a The islands of Cape Verde are to the west of the African mainland.
b Mauritius and the Seychelles are to the east and north-east of Madagascar
respectively.
Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in
Greenwich, London, counted from midnight. At different times in the past, it has
been calculated in different ways, including being calculated from noon;[1] as a
consequence, it cannot be used to specify a particular time unless a context is
given. The term 'GMT' is also used as one of the names for the time zone UTC+00:00
and,[2] in UK law, is the basis for civil time in the United Kingdom.[3][a]
English speakers often use GMT as a synonym for Coordinated Universal Time (UTC):
[4] in modern usage, this is incorrect – GMT is now a time zone, not a time
reference.[5][6] For navigation, it is considered equivalent to UT1 (the modern
form of mean solar time at 0° longitude); but this meaning can differ from UTC by
up to 0.9 s. The term GMT should not thus be used for purposes that require
precision.[7]
Because of Earth's uneven angular velocity in its elliptical orbit and its axial
tilt, noon (12:00:00) GMT is rarely the exact moment the Sun crosses the Greenwich
Meridian[b] and reaches its highest point in the sky there. This event may occur up
to 16 minutes before or after noon GMT, a discrepancy described by the equation of
time. Noon GMT is the annual average (i.e. "mean") moment of this event, which
accounts for the word "mean" in "Greenwich Mean Time".[c]
Originally, astronomers considered a GMT day to start at noon,[d] while for almost
everyone else it started at midnight. To avoid confusion, the name Universal Time
was introduced to denote GMT as counted from midnight.[8] Today, Universal Time
usually refers to UTC or UT1.[6]
The term "GMT" is especially used by United Kingdom bodies, such as the BBC World
Service, the Royal Navy, and the Met Office; and others particularly in Arab
countries, such as the Middle East Broadcasting Centre and OSN. It is a term also
used in other countries of the Commonwealth.
Contents
1 History
2 Ambiguity in the definition of GMT
3 GMT in legislation
3.1 United Kingdom
3.2 Other countries
4 Time zone

5 See also
6 Notes
7 References
8 Sources
9 External links
History
Main article: History of longitude
Greenwich clock with standard measurements
As the United Kingdom developed into an advanced maritime nation, British mariners
kept at least one chronometer on GMT to calculate their longitude from the
Greenwich meridian, which was considered to have longitude zero degrees, by a