What is Time Zone?
Time zone is each of the 24 time zones into which the Earth is divided, the 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 which hours should be added or subtracted accordingly.
The Greenwich meridian was adopted as a reference for establishing the time zone at the International Meridian Conference held in 1884 in Washington D.C. (United States). It represents the 0° degree of longitude of the Earth, whose imaginary line joins the poles.
What are time zones?
Time zones are each 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 makes the time vary between them, even if 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.
How is the time zone calculated?
Time zones are calculated by taking the Greenwich meridian as a reference, from 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, and each one represents one hour of the day. Therefore, if we add up each time zone, we 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 west-east rotation direction. Therefore, when we move towards the east, we must add hours, while if we move towards the west, we must subtract them.
In order to standardize the different time zones, the UTC system was created, which is considered the main time regulator.
What is the UTC system?
The time zone is based on Universal Time Coordinated (UTC), centered on the Greenwich Meridian, located near London, and replaces the old Greenwich Mean Time (GMT).
The acronym UTC is used to specify local times, either by adding or subtracting one or more hours depending on the time zones that exist between one place or another.
When we move from our point of origin to the east zone, hours are added (+hours) and the time zone is identified as UTC+. If we go to the west zone, hours (-hours) are subtracted and it is identified as UTC-. This logic is based on the rotational motion of the Earth and the consequent rising and setting of the sun.
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 o’clock in the morning.
Examples of UTC time zones
Among the countries located in the Greenwich Meridian or 0 meridian zone are:
- Spain (Canary Islands)
- Great Britain
- Portugal (not including the Azores)
- Chile (Chilean Antarctica and Magellan Region)
- Chile (Easter Island, Isla Sala y Gómez)
- Costa Rica
- Ecuador (Galapagos Islands)
- El Salvador
- Mexico (wide diversity of zones)
UTC- 9:00 A.M.
- United States (continental Alaska)
- France (French Polynesia)
- United States (Baker Islands, Howland Island)
- Saudi Arabia
- United Kingdom (British Indian Ocean Territory)
- Russia (Omsk)
- South Korea
- East Timor
- United States (Wake Islands)
- New Zealand
What is the time zone used for?
The main function of the time zone is to coordinate the times of all countries in order to organize the use of time and human activities.
Hence the need to establish time zones to better coordinate the different economic and transportation activities, among others, at national and international level. The first time zone calculations were developed between the 19th and 20th centuries, the most important being 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, which would seriously affect international relations and the great diversity of economic and social activities in the world.
The world clock is a tool for calculating time. These clocks automatically calculate the local time by adding or subtracting hours according to UTC. In addition, they have a system that takes into account the time change policy that some countries adopt to take advantage of sunlight (daylight saving time and winter time).
World clocks can be found in different locations and anyone can have one, since there are digital clocks specially designed for this function.
See also Greenwich Meridian.