See Earth-4 to see all this on the globe,  See the Time Zones of the world here

Degrees, Minutes and Seconds

As Earth is round, and a circle is also round, the Earth has been imaginarily divided into 360 degrees for the convenience of finding a location. Each degree is subdivided into Minutes, and each Minute is subdivided in Seconds. That is why when one wants to identify a location on the globe, he has to tell it in Degree, Minute and Second.

Longitude
The Longitude is the angular distance (in Degrees, Minutes and Seconds) of a point, East or West, of the prime meridian (Greenwich Time Line). These lines are often called Meridians. These are the imaginary lines going from North to South throughout the globe and are called Longitude. As a location needs two coordinates for its identification, to its aid are Latitude which run from West to East across the globe. To identify a location one has to write or tell both Longitude and the Latitude. These Longitude present two specialties -

Eastern Hemisphere and Western Hemisphere
Among these lines, Greenwich Line or Prime Meridian Line is the most important line from where the countdown of time begins. It has been fixed at the 0 Degree. It passes through London, UK. Towards its West are 90 Degrees West starting from 89, 88 West etc; and towards its East are also 90 Degree East starting from 89, 88 Degrees East etc. It passes through Greenwich (that is why it is called Greenwich Line also) is the central line which divides the globe in two parts - morning hours in Western side and evening hours in its Eastern side. Its location is at 0 Degree. Towards its East is Evening, from 12.00 AM to 12.00 PM  and towards its West it is Morning.

Time Zone
Longitude is the most important factor in deciding the time of the day - such as it is 4.00 PM or 9.00 AM at a particular place. Why? Because at every 1 Degree, 4 Minutes decrease towards West.

Remember there are 24 hours in a day, and the Sun takes 24 hours to go round the Earth, and Earth is round. That is why we have divided the Earth in 360 Degrees. Thus the Sun crosses these 360 Degrees in 24 hours (or 1,440 Minutes). If we divide 1440 Minutes by 360, it comes to 4 Minutes for each Degree. So, for example, if at the 40 Degree E Longitude it is 9.00 AM, then at 60 Degree E Longitude it should be 20 Degree X 4 minutes less (because 60 Degree is more towards West), means 80 Minutes early, means it should be 7.40 AM.

Longitude causes the time difference even in the same country if the country covers so many degrees. Small nations which do not cover many degrees, normally maintain the same time throughout their country, but the countries large enough like USA, Canada, USSR etc normally maintain Time Zones. For example USA has 6 Time Zones --
(1) Eastern Time Zone - -5 hours to Meridian -  if 12.00 PM is in London, Eastern Time Zone will have the time 7.00 AM,
(2) Central Time Zone - -6 hours to Meridian -  if 12.00 PM is in London, Eastern Time Zone will have the time 6.00 AM,
(3) Mountain Time Zone - -7 hours to Meridian -  if 12.00 PM is in London, Eastern Time Zone will have the time 5.00 AM,
(4) California Time Zone - -8 hours to Meridian -  if 12.00 PM is in London, Eastern Time Zone will have the time 4.00 AM,
(5) Alaska Time Zone - -9 hours to Meridian -  if 12.00 PM is in London, Eastern Time Zone will have the time 3.00 AM,
(6) Hawaii Time Zone - -10 hours to Meridian -  if 12.00 PM is in London, Eastern Time Zone will have the time 2.00 AM,

Latitude
The Latitude is an angular distance (in Degrees, Minutes and Seconds) point at the North or the South of the Equator. They are often called Parallel Lines too. These are the imaginary lines going from West to East. The main line is Equator which divides the Earth in half - Northern Hemisphere and Southern Hemisphere. This Equator line poses a few specialties in the the two areas divide by it.

(1) Northern and Southern Hemispheres -
Its one specialty is that the people living in Northern Hemisphere cannot see the stars of Southern hemisphere, because both Hemispheres have different sets of stars. Even the rotation of the earth cannot bring them at one another's place.

(2) Opposite Seasons -
Its another specialty is that seasons are opposite in each hemisphere. If there is Summer in Northern Hemisphere, there is Winter in Southern Hemisphere; and when there is Winter in Northern Hemisphere, there is Summer in Southern Hemisphere. The people feel odd when they travel between these hemispheres.
[I have always lived between 30-40 degree North, but once I had a chance to go Lesotho (a landlocked country in South Africa), located at 40 degree South. I stayed there for 1 year. I reached there in March after a long winter and as I reached there,  winter started after a month because of the Southern Hemisphere. All the time I continued to feel odd - May June and July were so cold.]

(3) No Time Change
Its third specialty is that time does not change on the same latitude, whether you are on 40 degree N in USA or on 40 Degree S in South America - because the time changes with the Longitude, not by Latitude.