What Are Time Zones and What Are They For?

time zone is each of the 24 time zones into which the Earth is dividedthe time it takes for the planet to rotate on its own axis, and which determines the time of a geographical area from the Greenwich meridian, from where hours must be added or subtracted as appropriate.

The Greenwich meridian was adopted as a reference to establish the time zone at the International Meridian Conference, held in 1884 in Washington DC (United States). It represents the degree 0° longitude of the Earth, whose imaginary line joins the poles.

What are time zones?

Time zone

The time zones are each one of the 24 imaginary lines that divide and establish the time of a particular geographic space. In theory they should be straight, however they are irregular due to the political borders between countries, which causes the hours to vary between them, even when they are on the same meridian.

In large countries such as Australia, Brazil, Chile, the United States, Mexico or Russia, several time zones have been implemented because they are territories that have more than one demarcated time zone.

What is the time zone used for?

The main function of the time zone is to coordinate the hours of all countries in order to organize the use of time and human activities.

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Hence, the need arose to establish time zones to better coordinate the different economic activities, transportation, among others, nationally and internationally. The first calculations of the time zones were developed between the 19th and 20th centuries, highlighting those made by Sandford Fleming.

If the time zone had not been established, it would be almost impossible to coordinate and organize the use of time, this would seriously affect international relations and the great diversity of economic and social activities in the world.

How is the time zone calculated?

The time zones are calculated taking as reference the Greenwich Meridianfrom which hours must be added or subtracted.

The longitude of each time zone is 15°, which represents a specific time for all cities, countries or regions located on the same meridian.

The Earth has 24 time zones, each representing an hour of the day. Therefore, if we add each time zone, we will obtain the 360° that the Earth measures

The time zone is directly related to the position of the Earth with respect to the sun and its direction of west-east rotation. Hence, when moving to the east, hours must be added, while if we move to the west, we must subtract them.

To standardize the different time zones, the UTC system was created, considered the main regulator of time.

What is the UTC system?

The time zone is based on Coordinated Universal Time or UTC. Universal Time, Coordinated), centered on Greenwich Mean Time, located near London, and replaces the old Greenwich Mean Time or GMT. Greenwich Mean Time).

The acronym UTC is used to specify local hours, either by adding or subtracting one or more hours depending on the time zones that exist between one place or another.

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When we move from our point of origin to the eastern zone, hours (+hours) are added and the time zone is identified as UTC+. If we were to go to the west zone, hours (-hours) are subtracted and it is identified as UTC-. This logic is based on the rotation movement of the Earth and the consequent birth and sunset.

This system is based on the measurements calculated by atomic clocks characterized by their great precision.

For example, if the time in Mexico City is UTC -5, assuming that it is noon in Greenwich, then five hours would have to be subtracted, that is, in Mexico City it would be seven in the morning.

Examples of UTC time zones

Among the countries that are located in the zone of the Greenwich meridian or meridian 0 are:


  • Spain (Canary Islands)
  • Britain
  • mali
  • Portugal (does not include the Azores Islands)
  • Guinea
  • Senegal

UTC- 3:00

  • Argentina
  • Brazil
  • Chile (Chilean Antarctic and Magallanes Region)
  • Paraguayan
  • Uruguay

UTC- 6:00

  • Chile (Easter Island, Sala y Gómez Island)
  • Costa Rica
  • Ecuador (Galapagos Islands)
  • The Savior
  • Honduras
  • Nicaragua
  • Mexico (wide diversity of areas)

UTC- 9:00

  • United States (mainland Alaska)
  • France (French Polynesia)

UTC- 12:00

  • United States (Baker Islands, Howland Island)


  • Saudi Arabia
  • Ethiopia
  • Madagascar
  • Turkey
  • Uganda


  • bangladesh
  • United Kingdom (British Indian Ocean Territory)
  • Russia (Omsk)

UTC+ 9:00

  • South Korea
  • Japan
  • East Timor

UTC+ 12:00

  • United States (Wake Islands)
  • fiji
  • New Zealand

World clock

The world clock is a tool for calculating time. These watches automatically calculate local time by adding or subtracting hours based on UTC. In addition, they have a system that takes into account the time change policy that some countries adopt to take advantage of sunlight (summer time and winter time).

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World clocks can be found in different locations and anyone can have one, as there are digital clocks specially designed for this function.

See also Greenwich Mean Time and AM and PM.