Notes on World Time Zones | Extra References > Social Studies > Class 9 | KULLABS.COM

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Notes, Exercises, Videos, Tests and Things to Remember on World Time Zones

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#### World Time Zones and Greenwich Mean Time

In the previous lesson, we knew that both latitudes and longitudes are used to locate places and countries precisely on the earth's surface.

There are altogether 360 longitudes on the earth, each representing a degree. The earth completes a rotation in a day i.e. 24 hours. This means it travels about 40000 km or 360° each day and each longitude in 4 minute difference from another nearest longitude. For convenient and practical international time relations, the earth in divided into 24 time zones with an interval of 15° that equals 1 hour. Following the establishment of the Royal Observatory Act at Greenwich in London in 1675, the longitude at Greenwich began to be used as their prime meridian by English cartographers. In 1884 a conference agreed to use this meridian as the prime meridian for all maps. Time zones are described as per their distance east or west of the prime meridian. As for this, every 15° eastward the time is 1 hour ahead because the earth moves west to east. Now the time was calculated in the base of GMT. It in mid-day (12:00 PM) at a place when the sun directly falls on its meridian. The shadow of an object in shortest at this moment of each day.

#### International Date Line

The international date line passes along the 180° longitude, except on inhabited islands in the pacific. It marks the place where travelers change their their date by 1 day on their voyage. East of the line (Western hemisphere) it is the one day earlier than to the west (Eastern hemisphere). The date line in curved eastwards and westwards to avoid crossing the land so that time relations in the region would not be complicated. Ponder over the trouble it might create if the line crossed over a small island in the pacific ocean.

• There are altogether 360 longitudes on the earth, each representing a degree.
• Following the establishment of the Royal Observatory Act at Greenwich in London in 1675, the longitude at Greenwich began to be used as their prime meridian by English cartographers.
• The international date line passes along the 180° longitude, except on inhabited islands in the pacific.
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### Questions and Answers

#### Click on the questions below to reveal the answers

As the question,

Madras at 80 degree EL is 3 p.m.

New York at 75 degree WL =?

The longitude of two places is (75 +180- 80)degree

=225 degree – 80 degree

=145 degree
In one degree longitude there will be 4 minutes.
In 145 longitude (145x 4) minutes i.e. 580 minutes.
580 minutes corresponds to 9 hours 40 minutes.
Therefore it will be 5:20 a.m.

New York lies at 75 degree EL

The difference of longitude of two places = (75 degree + 180 degree – 86 degree)

=255 degree-86 degree

=169 degree

In 1 degree longitude there will be 4 minutes.

In 169 degree longitude (169 degree x 4) there will be 676 minutes.

676 minutes or 11 hours 26 minutes

Therefore, If It’s 10 am in New York, as Nepal lie at EL. It is 100+ 11:26 = 21:26 P.M.

So, it will be 9:26 in Nepal.

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1776 AD
1675 AD
1778 AD
1877 AD

2 hour
3 hour
1 hour
4 hour

15 hour
24 hour
12 hour
18 hour

3 year
4 year
2 year
1 year

revolution
rotation
orbit
axis

orbit
rotation
revolution
axis
• ### An imaginary line of longitude on earth surface located at about 180 degrees of Greenwich meridian is

Prime meridian line
World time line
International Date Line
Hemisphere line
• ### The time eastward is ______ and westward is______

equal
fast, slow
slow, fast
none of the above
• ### The 24 world time zones (each representing 15 degree an hour) are described as per their

Distances of prime meridian
Distance of hemisphere lines
Distance of equator lines
Distance of world time

240
138
360
150

31,000 km
40,000 km
21,038 km
19,000 km
• ### Every 15 degree eastward the time is one hour ahead because the earth moves

East to west
East to south
West to east
North to south

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