How humanity came to the present time
45 years ago a day was first introduced extra “leap” second.
To use coordination, the 61st, the second was decided in order to make up the accumulated difference between the coordinated universal (UTC) and mean solar time. The latter largely depends on the speed of rotation of the earth, and it gradually declined and the gap between the familiar and the real solar time is becoming more noticeable.
How does the time in which we all live, where the easiest way to get “yesterday” and can “leap hour” to replace an additional second, to understand “news”.
Coordinated universal time
Coordinated universal time was introduced in 1964. It is referred to as UTC, however, this acronym doesn’t stand for anything — it was a compromise between the abbreviations from the English (CUT) and French (TUC) titles.
But the well-known measurement system Greenwich mean time (GMT) not really used since the late 1920-ies of XX century. On 1 January 1925 it was replaced by the World, or mean solar time (UT).
There are several versions of universal time, which differ in the method of its precise definition. UT0, for example, is determined by observation of stars and extragalactic radio sources (UT0). And the most common UT1 actually mean local solar time at longitude 0 degrees, but precisely because it is impossible to determine, UT1 is based on a complex system of additional calculations based on the angle at which the Earth rotates relative to the international celestial coordinate system.
It is based on UT1 later there was an international time standard UTC, which is determined at the atomic scale.
To do this, use an ultra-stable frequency reference oscillations of atoms moving from one energy state to another.
The keepers of time
The exact time in their work using atomic or quantum clocks. In addition, it is based on their data, almost all navigation systems in the world — from those that provide the movement of the spacecraft, ballistic missiles and aircraft, to automotive systems like GPS or GLONASS.
In the world there are only a few so-called centers of frequency standards, which set the atomic clock. They are located at the National Institute of standards and technology in Colorado, USA, National Institute of advanced industrial science and technology in Tokyo, the Federal physical technical Agency in Braunschweig German, the National laboratory of Metrology and tests in French Paris and the National physical laboratory in the British London.
Russia’s benchmark atomic clocks are in the all-Russian scientific research Institute of physical-technical and Radiotechnical measurements, which is located in the Moscow region village of Mendeleyevo.
To get in yesterday
Time zones United territory, which is as same as the real solar time, and as a result, the time difference with the UTC almost all turned out to be a multiple of one hour. But in some cases, the time difference becomes an important factor in relations with other countries or in the organization of life in the country — and then the usual division into zones is not valid.
So, a small Nepal in reality is in the same time zone, bordering the territory of India, but the Nepalese, specially introduced the small difference in time, which would allow them to not feel discomfort from differences with the solar time.
In the result, the Nepalese from the Indian time is different for 15 minutes, and the difference with UTC time is 5 hours and 45 minutes.
A similar situation exists on the Chatham archipelago, New Zealand: the time difference with the main territory of the state is 15 minutes, and the difference between archipelago and the UTC time is 12 hours and 45 minutes. In addition, the “special” time with a difference in 15 minutes are several villages in the West of Australia, where the difference with UTC is 8 hours and 45 minutes.
In China, by contrast, has decided to reduce the number of time zones for the convenience of governance. The territory of China located in five different time zones, but operates a single Beijing time. And if you cross the border of China and Afghanistan, you have to immediately set the clock for 3.5 hours.
A large number of time zones in one country, as a rule, is achieved due to the presence of outlying or overseas island territories is primarily concerned with the US, UK and France.
The largest number of mainland time zones — 11 — now used in Russia. Since 2011, the country introduced the concept of time zone, implying the legislature to establish a uniform time on site, which can be located in several time zones.
In addition, Russia is among the countries that are moving to the summer. In this case, all the time in the country temporarily offset from coordinated universal time.
In addition to summer and winter time (go to which was first introduced in 1917), Russia is the only country in the world where there is the concept of daylight saving time. It means real-time time zone plus one hour and was introduced in 1930 by the decree of SNK of the USSR. Decrees had already been abolished, so that the origin of the name still remains a mystery.
In history there are other cases when countries legally changed their time zones, but the uniqueness of the situation with maternity time is that when you change the time in multiple regions, time zones, formally remained the same through the phrase “plus one hour”. The transition itself, according to the decision of the CPC, carried out for a more rational use of daylight. In 1991 it was officially abolished.
Coordinated universal time synchronously with the appearance in the mid 1950-ies of atomic time, but also depends on the Sun, and accordingly, the rotation of the Earth.
However, the speed of rotation of our planet is gradually reduced, and this means that UTC needs to be adjusted. Watching this established in 1987, the international service of rotation of earth, which weekly reports the results of the observations and the deviation of UTC from mean solar time in a special Bulletin.
Since 1972, the accumulated difference can compensate by adding a day, an extra second on 30 June or 31 December. In addition, allowed the use of negative seconds — then the day will end at 23:59:59. In some cases, possible failures in the individual computer programs and applications, but in General the “leap” seconds do not affect the operation of the equipment.
The last time an extra second was put in on 31 December 2016.
Leap hours instead of leap seconds
It is not excluded that in the foreseeable future could be a new world reform time. In 2009 the international astronomical Union proposed to abandon the coordination of a second. Scientists explained this by the fact that the speed of rotation of the Earth becomes lower, and then add the “extra” second will have increasingly.
Alternatively, the astronomical Union has offered every 6 thousand years to add to universal coordinated time by one additional hour, however, is to take reform one of the “keepers of time” not in a hurry. In 2012 it was decided to postpone discussion of this issue in 2015, then 2017. Now further discussion on this matter is scheduled for 2023.