THE TIME ZONES

The time system

According to the movement of the Earth around the sun, the light of this star takes 24 hours to fall twice by the same point. By international convention, the Earth has been divided into 24 imaginary bands called time zones that establish the hourly system of the different countries 

• Each time zone comprises a zone bounded by two meridians displaced 15 ° from each other and corresponding to a time period of one hour. 
• All points within the same time zone have the same time.

Almost all the countries have adopted the official time defined by the time zones, that is to say, they have taken the Greenwich reference. The lines that mark the official time of each country are not totally coincident with the meridians since if the greater part of a country is included within a time zone, it is taken as the official hour of the same one that corresponds to that time zone and not respecting the exact form of the corresponding meridian. Some large countries (the United States, for example), can not keep the unified time for all their territory, so they must divide it into time zones

To know the time in some place of the world is taken as reference the Greenwich meridian. From there, one hour is added for each time zone that travels to the east and is delayed by one hour for each spindle that travels to the west.