The time zone or also called the time zone is each of the 24 parts into which the Earth is divided by means of meridians, starting at the Greenwich meridian, and which is used to determine the time in the days.
Since the Earth completes a rotation turn from west to east in 24 hours, all its points, in this period of time, pass one after another in front of the Sun. Noon is marked by the passage of the Sun through the meridian of a certain point. Thus, at the precise moment when it is noon in one place, the Sun will have already passed through all the points located in the East, and must still pass through all those located in the West.
Each time zone represents one hour of the day, and between one zone and the next there is a difference of one hour. Therefore, only the points that belong to a meridian will have the same time, each time zone to the east of your position is one hour later, and to the west it would be one hour earlier.
Likewise, if we divide the 360 geographic meridians (one for each degree of the earth's circumference) by 24 (the hours of the day), we will obtain that in each hour that passes, the Sun will have traveled 360/24 = 15 meridians; that is, one meridian every 4 minutes.
Time zones allow you to set the legal time. However, the official time of a region of a country does not always coincide with its corresponding time according to international time zones. The governments of different countries by legal decision establish the official schedules from the time zone in which the capital is included, or they modify them seasonally for socioeconomic reasons (time changes in spring and autumn).
There are countries that have more than one official time because the extension of their territories is large and because of their location with respect to the tropics, thus covering several time zones. Many of them adopt three or more spindles, the best known are: Brazil (3), United States of America (7), Russia (11), Australia (3), China (5), Spain (2), among others.
The international date line is the Greenwich Antimeridian. This line, for practical reasons, runs more or less along the 180º meridian, from the Bering Strait across the entire Pacific Ocean heading south.
This line of date change along with the Greenwich meridian, divides the earth into two hemispheres, which on the same day have two different dates, except at the time when it is noon in Greenwich, in this case the date is uniform all the planet. If a person crosses the west date line, they will lose a day; If you cross it to the east, you will win one day
