Until now, in the computer settings of Windows, the time zone is set by the abbreviation GMT. What is it and how does it relate to the modern UTC time coordination system? We will talk about this in our article. Not everyone can determine the time at a location point relative to Greenwich. But we will try to clarify this issue in a popular language. First of all, you need to answer the question: "GMT - what is this?" How is this abbreviation deciphered?
British snobbery
In the old days, time was set in the afternoon. When the sun was at its zenith, that is, it reached its highest point in the visible horizon, it was believed that it was twelve o'clock in the afternoon. With the development of international trade, the need arose to coordinate time into a single system. The reference point was the zero meridian. It passes through the Royal Observatory in the town of Greenwich, near London.
Thus, the abbreviation GMT stands for Greenwich Mean Time. All territories located west of Greenwich lag behind its time, while those located to the east are ahead of it. There is another significant meridian on the surface of planet Earth. This is a date line. The territory located east of it lives (in the literal sense of the word) yesterday. In 1972, the new abbreviation UTC changed GMT. What time is it? The abbreviation stands for "Coordinated Universal Time."
Time Zones
In Russian metrology, the abbreviation SGV is used instead of GMT. What is it? Letters are deciphered as "Average geographical time." But again, we can’t get away from Greenwich. After all, the whole world counts the hours from the zero meridian. If you are punctual and accurately determine the time for each point on the globe, you need to know its remoteness from Greenwich to the west or east. And Coordinated Universal Time (in other words, UTC) displays basically noon in certain countries (or parts of them). If GMT is a time that knows no political borders, then time zones often extend to the whole state (if it does not extend very much from west to east). Thus, UTC + 0 is not the time at the Greenwich Observatory and at the zero meridian, but throughout the UK and Ireland, as well as Iceland, Portugal, Morocco, etc. But the calculation of hours using the TCB system is carried out according to the same principle as in GMT.
Summer and winter time
In countries lying in high latitudes, daylight hours vary greatly depending on the time of year. Therefore, the northern countries often switch to summer time. Residents of these states shift the clock hands an hour ahead. This happens on the last Sunday of March. The United Kingdom is also on the list of countries practicing summer hours. But the true noon from April to October is then observed at one o'clock in the afternoon, because the average GMT time does not depend on the season.
Countries lying near the equator, where the daylight hours at any time of the year are approximately twelve hours, do not shift the arrows seasonally. They constantly live in winter (true) time. On this basis, the Russian Federation also decided not to move the hands annually an hour ahead. By the way, another country lying in high latitudes refused to switch to daylight saving time. This is Iceland. The island nation lives according to Greenwich Mean Time (GMT + 0). Great Britain and Ireland lying at approximately the same meridian are in UTC + 0 in winter and in UTC + 1 in summer.
What are UTC and GMT for?
Time is a concept that loves precision. For coordinated actions, dispatching services located at points remote from each other on the Earth need to know how many hours, minutes and seconds are. Also, the need for a coordinated time and have broadcasters of various frequencies. UTC is necessary to establish a specific standard for navigational and scientific purposes. Throughout the nineteenth century, sailors of the British fleet, plowing the oceans, calculated the time using GMT. Moving west of Greenwich, they took the clock, and to the east they pounded. According to this principle, the globe is now divided into time zones. For example, Vladivostok time corresponds to GMT + 11, Georgian - GMT + 4, Hawaiian-Aleutian - GMT-10, Moscow - GMT + 4, Standard Eastern Time (it is used for New York and the United States and Canada adjacent to the Atlantic Ocean, and also in Jamaica, Panama, Haiti, Bahamas) - GMT-5.