Wherever you live, the time of day
is somewhat determined by when the sun rises and sets.However, because of the Earth’s rotation, the
sun does not rise and set at the same time all over
the world.So
when it is midday where you live, it is midnight somewhere
on the other side of the world.This means that your local time is not necessarily the same
as someone else’s local time.
So how do we determine what time
it is in any given part of the world ?Who makes the rules for the calculations we use
?
History
Until
1883, each country and in a lot of cases territories
within countries used their own local times in
correspondence and schedules etc.This became very complicated and confusing
to all involved and in 1883 an international agreement
was reached which divided the world into 24 time
zones (each zone made up of 15°
of longitude).As part of this agreement, the Greenwich
Observatory in London was designated as longitude
0°
- the base position for the Standard Time system.
GMT
The
local time in Greenwich is known as Greenwich
Mean Time (GMT). All of the worlds time
zones are measured relative to GMT and are described
by their distance east or west of Greenwich.
Time
Zones
The area where you live has its own time zone.
This time zone can be roughly determined by calculating
the number of 15°
offsets (longitude) between where you live and
Greenwich. Look at a map of the world and
divide it into 24 equal parts; each part being
15°
of longitude :
Longitude
and Meridians
A
line of longitude and a meridian are the same
thing.
Both
of these terms are used to describe an imaginary
line on the Earth’s surface which stretches from
the North pole to the South pole.
The Greenwich Observatory is
designated as 0°
longitude. 0°
longitude is also know as the Prime Meridian.
At the time when the sun is directly
over the line of longitude where you are then
it is midday.
Now
count the number of zones between you and Greenwich.
This is the number of hours your time zone is offset
from GMT. If you are East of Greenwich then the
offset is ahead of GMT. If you are West of Greenwich
then the offset is behind GMT.
If
you live in the same time zone as someone else then
your local time is the same as theirs. ie. Your
clock will be set to the same time as theirs.
This is true even if they are on the opposite side of
the country (but within the same time zone).
International
Date Line
In
reality, the time zones of the world are not equal in
size or regular in shape. The boundaries of each
time zone is bent to accomodate international boundaries
and regions within countries.
The
International Date Line marks the place on the globe
where you cross from being ahead of GMT to being behind
GMT (and vice versa). If you cross the line from
East to West, you add a day to your calendar.
If you cross from West to East, you subtract a day from
your calendar.
The
International Date Line is situated near 180° longitude
and bends around countries so as not to cross land.
Special
Time Zones
Time zone information does change.
For example the Australian Federal government changed
the start date for daylight savings in the year 2000
especially for the summer Olympics.
So,
how do you find out what time it is anywhere in
the world ?
WorldTimer 5 from Castle Software
is a user configurable world clock that can display
a number of clocks in different time zones. As well
as changing the label and timezone of each clock, the
user may change the background colour and the text colour
and font to suit their individual tastes. Clocks may
be digital or analog and a combination of both may be
displayed at the same time.
A world map can be displayed and
optionally the world time zones and day/night regions
can be superimposed on this map. It is also possible
to configure countdown clocks to countdown to an event
of your choice.
WorldTimer has the ability to synchronize
your system clock to the correct time using SNTP over
the internet.
For more details, have a look at
the WorldTimer
page on the Castle Software web site.
The
World's Time Zones
The main time zones of the world,
and some of the areas within these time zones are listed
below (in alphabetical order by
Time Zone Name) :
Time
Zone Name
Offset
from GMT
Areas
in Time Zone
Afghanistan Standard Time
+04:30
Kabul
Alaskan Standard Time
-09:00
Alaska
Arab Standard Time
+03:00
Kuwait, Riyadh
Arabian Standard Time
+04:00
Abu Dhabi, Muscat
Arabic Standard Time
+03:00
Baghdad
Atlantic Standard Time
-04:00
Atlantic Time (Canada)
AUS Central Standard Time
+09:30
Darwin
AUS Eastern Standard Time
+10:00
Canberra, Melbourne, Sydney
Azores Standard Time
-01:00
Azores
Canada Central Standard
Time
-06:00
Saskatchewan
Cape Verde Standard Time
-01:00
Cape Verde Is.
Caucasus Standard Time
+04:00
Baku, Tbilisi, Yerevan
Cen. Australia Standard
Time
+09:30
Adelaide
Central America Standard
Time
-06:00
Central America
Central Asia Standard Time
+06:00
Astana, Dhaka
Central Europe Standard
Time
+01:00
Belgrade, Bratislava, Budapest, Ljubljana, Prague
Central European Standard
Time
+01:00
Sarajevo, Skopje, Sofija, Vilnius, Warsaw, Zagreb
Central Pacific Standard
Time
+11:00
Magadan, Solomon Is., New Caledonia
Central Standard Time
-06:00
Central Time (US & Canada)
China Standard Time
+08:00
Beijing, Chongqing, Hong Kong, Urumqi
Dateline Standard Time
-12:00
Eniwetok, Kwajalein
E. Africa Standard Time
+03:00
Nairobi
E. Australia Standard Time
+10:00
Brisbane
E. Europe Standard Time
+02:00
Bucharest
E. South America Standard
Time
-03:00
Brasilia
Eastern Standard Time
-05:00
Eastern Time (US & Canada)
Egypt Standard Time
+02:00
Cairo
Ekaterinburg Standard Time
+05:00
Ekaterinburg
Fiji Standard Time
+12:00
Fiji, Kamchatka, Marshall Is.
FLE Standard Time
+02:00
Helsinki, Riga, Tallinn
Standard Time
GMT
Greenwich Mean Time : Dublin, Edinburgh, Lisbon,
London
Greenland Standard Time
-03:00
Greenland
Greenwich Standard Time
GMT
Casablanca, Monrovia
GTB Standard Time
+02:00
Athens, Istanbul, Minsk
Hawaiian Standard Time
-10:00
Hawaii
India Standard Time
+05:30
Calcutta, Chennai, Mumbai, New Delhi
Iran Standard Time
+03:30
Tehran
Israel Standard Time
+02:00
Jerusalem
Korea Standard Time
+09:00
Seoul
Mexico Standard Time
-06:00
Mexico City
Mid-Atlantic Standard Time
-02:00
Mid-Atlantic
Mountain Standard Time
-07:00
Mountain Time (US & Canada)
Myanmar Standard Time
+06:30
Rangoon
N. Central Asia Standard
Time
+06:00
Almaty, Novosibirsk
Nepal Standard Time
+05:45
Kathmandu
New Zealand Standard Time
+12:00
Auckland, Wellington
Newfoundland Standard Time
-03:30
Newfoundland
North Asia East Standard
Time
+08:00
Irkutsk, Ulaan Bataar
North Asia Standard Time
+07:00
Krasnoyarsk
Pacific SA Standard Time
-04:00
Santiago
Pacific Standard Time
-08:00
Pacific Time (US & Canada,; Tijuana)
Romance Standard Time
+01:00
Brussels, Copenhagen, Madrid, Paris
Russian Standard Time
+03:00
Moscow, St. Petersburg, Volgograd
SA Eastern Standard Time
-03:00
Buenos Aires, Georgetown
SA Pacific Standard Time
-05:00
Bogota, Lima, Quito
SA Western Standard Time
-04:00
Caracas, La Paz
Samoa Standard Time
-11:00
Midway Island, Samoa
SE Asia Standard Time
+07:00
Bangkok, Hanoi, Jakarta
Singapore Standard Time
+08:00
Kuala Lumpur, Singapore
South Africa Standard Time
+02:00
Harare, Pretoria
Sri Lanka Standard Time
+06:00
Sri Jayawardenepura
Taipei Standard Time
+08:00
Taipei
Tasmania Standard Time
+10:00
Hobart
Tokyo Standard Time
+09:00
Osaka, Sapporo, Tokyo
Tonga Standard Time
+13:00
Nuku'alofa
US Eastern Standard Time
-05:00
Indiana (East)
US Mountain Standard Time
-07:00
Arizona
Vladivostok Standard Time
+10:00
Vladivostok
W. Australia Standard Time
+08:00
Perth
W. Central Africa Standard
Time
+01:00
West Central Africa
W. Europe Standard Time
+01:00
Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna
West Asia Standard Time
+05:00
Islamabad, Karachi, Tashkent
West Pacific Standard Time
+10:00
Guam, Port Moresby
Yakutsk Standard Time
+09:00
Yakutsk
The main time zones of the world, and some
of the areas within these time zones are listed below
(in order of Offset from GMT)
:
Time
Zone Name
Offset
from GMT
Areas
in Time Zone
Dateline Standard Time
-12:00
Eniwetok, Kwajalein
Samoa Standard Time
-11:00
Midway Island, Samoa
Hawaiian Standard Time
-10:00
Hawaii
Alaskan Standard Time
-09:00
Alaska
Pacific Standard Time
-08:00
Pacific Time (US & Canada,; Tijuana)
Mountain Standard Time
-07:00
Mountain Time (US & Canada)
US Mountain Standard Time
-07:00
Arizona
Canada Central Standard
Time
-06:00
Saskatchewan
Central America Standard
Time
-06:00
Central America
Central Standard Time
-06:00
Central Time (US & Canada)
Mexico Standard Time
-06:00
Mexico City
Eastern Standard Time
-05:00
Eastern Time (US & Canada)
SA Pacific Standard Time
-05:00
Bogota, Lima, Quito
US Eastern Standard Time
-05:00
Indiana (East)
Atlantic Standard Time
-04:00
Atlantic Time (Canada)
Pacific SA Standard Time
-04:00
Santiago
SA Western Standard Time
-04:00
Caracas, La Paz
Newfoundland Standard Time
-03:30
Newfoundland
E. South America Standard
Time
-03:00
Brasilia
Greenland Standard Time
-03:00
Greenland
SA Eastern Standard Time
-03:00
Buenos Aires, Georgetown
Mid-Atlantic Standard Time
-02:00
Mid-Atlantic
Azores Standard Time
-01:00
Azores
Cape Verde Standard Time
-01:00
Cape Verde Is.
Standard Time
GMT
Greenwich Mean Time : Dublin, Edinburgh, Lisbon,
London
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