Each time zone measures 15 degrees, which results from dividing the 360 degrees of the earth’s sphere by 24, which is the number of hours it takes for the Earth to turn its own axis and which constitutes the measure of a day on the planet. .
The 15 degrees that each time zone measures represent one hour, which will be calculated according to its direction (east or west) in relation to the Greenwich meridian. Therefore, the 24 spindles correspond to 24 hours of the day.
How time zones are calculated
The 24 time zones are governed by a time standard called UTC (Coordinated Universal Time), which is obtained in turn from International Atomic Time, a scientific standard that measures time from atomic clocks found in various parts of the planet. , and which has so far turned out to be the most accurate.
The planet’s time zones are calculated using a single reference: the zero meridian or Greenwich meridian, located in London. From the zero meridian to the east, one hour is added to each zone according to what the UTC standard dictates.
On the other hand, the time zones that are from the Greenwich meridian to the west are subtracted by one hour each.
The reason for this is that the Earth rotates in that direction (from west to east). For this reason, the hourly calculation of the time zones that travel in that direction is called positive deviation, while the calculation of time zones that go in the opposite direction (to the west) is called negative deviation.
Examples of time zones
Quickly calculating the time of a certain region or city knowing its time zone, remembering that if the zone is negative, the hours are subtracted and if they are positive, they are added. These are some examples:
It is the time zone that corresponds to the zero meridian, or Greenwich meridian. Some countries or areas that share this zone are:
- Ivory Coast
- Portugal (except the Azores islands)
- United Kingdom (including Great Britain, Northern Ireland, Isle of Man, Channel Island, Guernsey and Saint Helena, Tristan da Cunha and Ascension, located in Africa)
UTC -05:00 (five hours behind)
It is the time zone of:
- Some regions of Brazil and the United States.
In this case the spindle is negative, it means that 5 hours must be subtracted from the time indicated by the Greenwich meridian. Therefore, if in the localities that are located on that meridian it is 8 at night (London time, for example), in all the regions that correspond to the UTC -5 time zone it would be 3 in the afternoon.
UTC -12:00 (twelve hours less)
It is the time zone of two American islands:
- Baker Island
- Holland Island
If on the zero meridian it is 6 in the afternoon, on those islands it is 6 in the morning.
UTC +06:00 (six more hours) :
It is the time zone of:
- Bhutan, among others.
If on the zero meridian it is 8 in the morning, in the countries mentioned it will be 4 in the afternoon
What are time zones for?
Time zones are necessary to organize time around the world. Previously, the hours were based on different meridians depending on what the authorities of each country or locality decided, and this brought a series of consequences in daily life.
With the creation of the spindle system, the time measurement of the 24 time zones is governed from the zero meridian, and having a single origin, the calculation of the time in each place becomes easier and more practical.