Time Zone

At different places around the earth, the sun is directly overhead at different times compared to when the sun is overhead at the Prime meridian at Greenwich.

In order that places with similar longitude could share a common standard time and so that the sun could be overhead at approximately 12noon all around the world, the earth is divided into zones of different time (time zones).

Each timezone can be identified by how many hours different that the zone's time is from UT.

Conventionally, timezones to the East of Greenwich are considered negative and timezones to the West of Greenwich are considered positive.

In this program, timezones are identified by a number between -13 to 12 inclusive.

Example

City/Timezone	Timezone
Hawaii	+10 gives UT
Alaska	+9 gives UT
Pacific Time (US & Canada)	+8 gives UT
Mountain Time (US & Canada)	+7 gives UT
Central Time (US & Canada)	+6 gives UT
Eastern Time (US & Canada)	+5 gives UT
Greenland	+3 gives UT
London	0
Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna, Belgrade, Budapest, Prague	-1 gives UT
Athens, Istanbul, Minsk, Cairo, Pretoria, Helsinki, Jerusalem	-2 gives UT
Moscow	-3 gives UT
Ekaterinburg, Islamabad, Karachi, Tashkent	-5 gives UT
Calcutta, Mumbai, New Delhi	-5.5 gives UT
Almaty	-6 gives UT
Bangkok, Hanoi, Jakarta	-7 gives UT
Beijing, HongKong, Kuala Lumpur, Singapore, Perth	-8 gives UT
Tokyo, Seoul	-9 gives UT
Adelaide, Darwin	-9.5 gives UT
Brisbane, Sydney, Melbourne, Lismore	-10 gives UT
Auckland, Wellington	-12 gives UT
Nuku'alofa	-13 gives UT

NOTE WELL: In the clock utility of Microsoft Windows, and most common sources, Eastern Time (US and Canada) is referred to by notation "GMT-5". This is exactly opposite to the notation that this program uses. The notation that this program uses for Eastern Time (US and Canada) is "+5 gives UT".

Calculate it!

The Sun API functions that require the entry of a point of time require the entry of timezone so that UT may be calculated.