What is UTC or Greenwich Mean Time? Utc – universal coordinated time.

Standard time is a system of counting time based on dividing the Earth's surface into 24 time zones, every 15° in longitude. Time within the same time zone is considered the same. In 1884, on International conference it was decided to use this system. In accordance with the international agreement of 1883, the prime (“zero”) meridian is considered to be the one that passes through the Greenwich Observatory in the suburbs of London. Local Greenwich Time (GMT) has been agreed to be called Universal Time or “World Time” UTC/GMT/Z.

On the territory of Russia, since March 28, 2010, there are 9 time zones (before that there were 11 time zones). Samara Region and Udmurtia switched to Moscow time(second time zone). Kemerovo region. (Kuzbass) – to Omsk (MCK+3). Kamchatka Territory and Chukotka - to Magadanskoye (MSK+8). In these five subjects of the Federation, on March 28, 2010, the clock hands were not moved.

Two belts are being abolished - the third (Samara, MSK+1) and the eleventh (Kamchatsky, MSK+9). There are 9 of them in total, and the maximum time range in our country is reduced from 10 to 9 hours.

In Russia, since March 2011, after the transition to summer time, the clock hands will no longer move.

Time zone of Moscow, according to stable time: +4 (UTC/GMT + 4:00)

UTC (coordinated universal time) is a worldwide standard for determining time and date. It was formerly known as Greenwich Mean Time (GMT). Other abbreviations related to this standard are "universal time" and "world time."
Why do you need UTC time?

UTC is used by international shortwave broadcasters in their frequency schedules and programming plans. Amateur radio broadcasters, shortwave listeners, military, and service radio services also widely use UTC. Greenwich Mean Time was based on the time on the Prime Meridian, which passes through Greenwich, England. GMT became the world time and date standard because it was used by the British Royal Navy and Merchant Marine during the nineteenth century. Today, precision atomic clocks, shortwave time signals, and satellites operate using UTC to ensure a reliable and accurate standard for scientific and navigational purposes. Although there are refinements in precision, the UTC standard uses the same principles as GMT.
What time system does UTC use?

UTC uses a 24-hour time notation system. "1:00 AM" in UTC is expressed as 0100 and declared as "zero one hundred". Fifteen minutes past two is expressed as 0115; thirty-eight minutes past two - 0138 (usually pronounced "zero one thirty-eight"). The next minute after 0159 is 0200. The next minute after 1259 is 1300 (pronounced “thirteen hundred”). This continues until 2359. The next minute is 0000 (“zero hundred”) - the beginning of a new day.
Which main mistake when recalculating time?

The main source of confusion when using UTC is that the date also changes according to UTC. For example, a QSO conducted on Friday at 23:00 UTC in Moscow will be recorded on Saturday at 3:00 Moscow time. And vice versa, if you made a QSO in Moscow on Monday 3:00 MT, the log should indicate “Sunday, 23:00 UTC.

Satellite navigators, computer clocks, and all world transport use UTC time as a reference point in the world. What it is and how it differs from GMT interests everyone who is not a geography specialist.

Time Zones

Until the middle of the 19th century, time in different settlements with different longitudes was set chaotically, with a reference point to the moment of sunrise and sunset. With development modern species transport (primarily railway) and the acceleration of the pace of cargo transportation, the need arose to set time standards.

As a result, in some states an attempt was made to establish a uniform time - most often the capital was taken as the starting point. However, such a step was categorically unacceptable for huge multinational empires on which “the sun never set.” The latest achievements of geography and astronomy at that time came to the rescue.

Due to the rotation of the Earth around its axis, the onset of a sunny day in different places the world is not the same. To correct for this astronomical phenomenon, it was introduced concept of time zones. To do this, the entire globe was conditionally divided into 24 time zones of 15 degrees, within which it was agreed to consider time to flow equally. The Greenwich meridian was taken as the zero meridian. Obviously, when approaching the poles, the meaning of time zones is lost, and the so-called universal time is counted there.

Within each geographic time zone (or time zone), the so-called standard time operates - that is, the time of the meridian that divides this zone in half. The moment of the upper culmination of the Sun on this meridian occurs at approximately 12-00, with an error of half an hour.

What is an administrative time zone?

However, geographical time zones are often not very convenient for use for administrative purposes. This is not surprising: state borders never run exactly along the meridians. Therefore, for convenience, the limits of time zones have been changed, adjusted for state borders or large natural or man-made barriers such as:

• Rivers;
• Mountain systems;
• Railways;
• Borders between countries or territorial units of one state;
• Proximity to the capital also matters: for example, Moscow time operates in many regions of the Volga region, although it has nothing to do with solar time there. However, this can be justified by the needs of business connected with Moscow;
• Political considerations: for example, in 2014, Moscow time was adopted by the Republic of Crimea. And vice versa, after the collapse of the USSR, the young state of Ukraine, in order to distance itself from yesterday’s “big brother”, pointedly moved its arrows closer to Europe.

In Russia, standard time was approved in 1919 after the communists came to power. Before that, a single standard St. Petersburg time was in effect for communication and transport workers.

Reforms of temporary zones in our country were inconsistent and extremely ill-conceived. For example, in 2010, by decree of the President of Russia, the number of time zones was reduced to nine. However, the step turned out to be so unpopular (dawn in a number of regions began in the middle of the night) that it forced the federal authorities to return next year people are in 11 time zones when winter time is frozen. Because of this, it began to get dark early in a number of regions.

In 2016, several entities again changed their hourly registration.

Thus, the whole world is divided into 24 time zones, but in each country, with the stroke of a pen, the local government can change the established standard time. In addition, in some countries there is a transition to summer and winter time, in others (which includes Russia, where permanent summer time was established in 2014) - not.

All this does not add order to chronological orientation and would completely lead to chaos if it were not agreed for certain purposes - mainly for the needs of transport and communication services - to use universal time and its derivatives.

The concept of “universal time” in different contexts can be understood as:

• Time, which is counted based on observation of the position of the Moon, stars and other astronomical objects (abbreviated as UT0);
• UT1- time at the Greenwich meridian adjusted for the rotation of the Earth relative to active galactic nuclei;
• UT1R- a refined version of the previous formula, only adjusted for the effect of ebbs and flows on the planet’s rotation rate;
• UT2R- an improved version of the above time, with clarification of various seasonal changes, movements of lithospheric plates, etc., despite the fact that it is highly accurate, it is not used almost anywhere.
• UTC- is based on the UT1 formula, but adjusted for international atomic time.

Usually, Universal time is the last time listed in the list - UTC . Interestingly, there is no specific decoding of the abbreviation. These letters were simply chosen for ease of perception in different countries.

Atomic time: what is it?

Atomic clocks are considered the most accurate chronometer today. The error they provide is so small that it needs to be corrected approximately every few tens of millions of years. Their work, as the name clearly suggests, is based on effects occurring at the atomic level. It is the atomic clock that is used as the most reliable reference point by precision time services around the world.

It is not surprising that based on the readings of this chronometer, the so-called International Atomic Time (AT) was introduced. Its accuracy is ensured by almost four hundred atomic clocks scattered across fifty research centers around the world. Most laboratories have a cesium clock at their disposal.

All indicators are sent to the Chamber of Weights and Measures, which is located in France, where, after processing the data, the weighted average world time is made publicly available.

What does UTC mean?

UTC standard - universal coordinated time, it is based on both atomic time and UT1. I couldn't find the latest standard wide application because of its intermittency. Once a year, the so-called coordination second is added to UTC to level the values ​​between the two formulas.

This standard is used:

• In aviation;
• In satellite positioning (GLONASS, GPS);
• In weather forecasting;
• On the International Space Station;
• At the Earth's poles;
• In tachographs (a computer that is installed on vehicle to track the condition of the vehicle and monitor the crew);
• In amateur radio broadcasting.

It is UTC that today is the reference point in standard time around the world: accordingly, Greenwich time is set as UTC±0, and the rest are obtained by adding numbers (up to 12) or subtracting (also up to 12).

What is the difference between UTC and GMT?

GMT, or Greenwich Mean Time, was in use until the 70s of the last century instead of the UTC standard and was used for the same purposes - namely as a chronological reference point.

Unlike modern coordinated time, Greenwich time was not based on advanced technologies in the form of atomic clocks, but was the so-called solar time. GMT had in its database astronomical observations of the rotation of our planet relative to the celestial bodies.

In domestic practice of navigation and geography, GMT is often referred to as SGV ( GMT/GMT).

Currently, GW and UTC are often mistakenly used as synonyms, although the basic methodology of each standard is fundamentally different.

More than forty years ago, the UTC standard was introduced throughout the world. What is this? There is only one answer to this question - this is world chronological standard.

Video about UTC time zone

In this video, physicist Vladimir Orekhov will tell and show how the Earth is divided into time zones, and how the UTC format appeared:

Time difference with countries of the world, regions of Russia and Moscow.

Nowadays, time is set using Coordinated Universal Time (UTC), which was introduced to replace Greenwich Mean Time (GMT). The UTC scale is based on the uniform atomic time scale (TAI) and is more convenient for civilian use. around the globe are expressed as positive and negative offsets from UTC. It should be remembered that UTC time is not converted either in winter or summer. Therefore, for those places where there is a change to daylight saving time, the offset relative to UTC changes.

Principles of differentiation
The basis modern system Coordinated universal time (universal time) is established, on which the time of all depends. In order not to enter local time for each degree (or each minute) of longitude, the Earth's surface is conventionally divided by 24. When moving from one to another, the values ​​of minutes and seconds (time) are preserved, only the value of the hours changes. There are some countries in which local time differs from world time not only by a whole number of hours, but also by an additional 30 or 45 minutes. True, such time zones are not standard.

Russia - 11 time zones;
Canada - 6 time zones;
USA - 6 time zones (including Hawaii, excluding island territories: American Samoa, Midway, Virgin Islands, etc.);
in the autonomous territory of Denmark - Greenland - 4 time zones;
Australia and Mexico - 3 time zones each;
Brazil, Kazakhstan, Mongolia and Democratic Republic Congo - 2 time zones.
The territories of each of the remaining countries in the world are located in only one time zone.

Despite the fact that the territory of China is located in five theoretical zones, a single Chinese standard time operates throughout its entire territory.

The only administrative-territorial unit in the world whose territory is divided into more than two is the Republic of Sakha (Yakutia), which is a subject of the Russian Federation (3 time zones).

In the USA and Canada, the borders are very winding: there are often cases when they go through a state, province or territory, since territorial affiliation with a particular zone is determined at the levels of administrative-territorial units of the second order.

UTC-12 - International Date Line
UTC-11 - Samoa
UTC-10 - Hawaii
UTC-9 - Alaska
UTC-8 - North American Pacific Time (USA and Canada)
UTC-7 - Mountain Time (USA and Canada), Mexico (Chihuahua, La Paz, Mazatlan)
UTC-6 - Central Time (USA and Canada), Central American Time, Mexico (Guadalajara, Mexico City, Monterrey)
UTC-5 - North American Eastern Time (USA and Canada), South American Pacific Time (Bogota, Lima, Quito)
UTC-4:30 - Caracas
UTC-4 - Atlantic Time (Canada), South American Pacific Time, La Paz, Santiago)
UTC-3:30 - Newfoundland
UTC-3 - South American Eastern Time (Brasilia, Buenos Aires, Georgetown), Greenland
UTC-2 - Mid-Atlantic Time
UTC-1 - Azores, Cape Verde
UTC+0 - Western European Time (Dublin, Edinburgh, Lisbon, London, Casablanca, Monrovia)
UTC+1 - Central European Time (Amsterdam, Berlin, Bern, Brussels, Vienna, Copenhagen, Madrid, Paris, Rome, Stockholm, Belgrade, Bratislava, Budapest, Warsaw, Ljubljana, Prague, Sarajevo, Skopje, Zagreb) Western Central African Time
UTC+2 - Eastern European Time (Athens, Bucharest, Vilnius, Kiev, Chisinau, Minsk, Riga, Sofia, Tallinn, Helsinki, Kaliningrad), Egypt, Israel, Lebanon, Turkey, South Africa
UTC+3 - Moscow time, East African time (Nairobi, Addis Ababa), Iraq, Kuwait, Saudi Arabia
UTC+3:30 - Tehran time
UTC+4 - Samara time, United United Arab Emirates, Oman, Azerbaijan, Armenia, Georgia
UTC+4:30 - Afghanistan
UTC+5 - Yekaterinburg time, West Asian time (Islamabad, Karachi, Tashkent)
UTC+5:30 - India, Sri Lanka
UTC+5:45 - Nepal
UTC+6 - Novosibirsk, Omsk time, Central Asian time (Bangladesh, Kazakhstan)
UTC+6:30 - Myanmar
UTC+7 - Krasnoyarsk time, Southeast Asia(Bangkok, Jakarta, Hanoi)
UTC+8 - Irkutsk time, Ulaanbaatar, Kuala Lumpur, Hong Kong, China, Singapore, Taiwan, Western Australian time (Perth)
UTC+9 - Yakut time, Korea, Japan
UTC+9:30 - Central Australian Time (Adelaide, Darwin)
UTC+10 - Vladivostok time, Eastern Australian time (Brisbane, Canberra, Melbourne, Sydney), Tasmania, Western Pacific time (Guam, Port Moresby)
UTC+11 - Magadan time, Central Pacific time (Solomon Islands, New Caledonia)
UTC+12 - Kamchatka time, Marshall Islands, Fiji, New Zealand
UTC+13 - Tonga
UTC+14 - Line Islands (Kiribati)

Before the introduction of standard time, each city used its own local time. solar time, depending on geographic longitude. The standard time system was adopted in the late 19th century as an attempt to end the confusion caused by each locality using its own solar time. The need to introduce such a standard became extremely urgent with the development of the railway, if train schedules were compiled according to the local time of each city, which caused not only inconvenience and confusion, but also frequent accidents. This was especially true for large territories connected by a railway system.

Before the invention of the railroad, traveling from one place to another took so much time. When traveling, time would only need to be advanced by 1 minute every 12 miles. But with the advent of the railroad, which made it possible to travel hundreds of miles a day, timing became a serious problem.

Great Britain

Britain was the first country to decide to establish one standard time for the entire country. The British Railways were more concerned with the problem of local time inconsistency, which forced the government to unify time throughout the country. The original idea belonged to Dr. William Hyde Wollaston (1766-1828) and was taken up by Abraham Follett Osler (1808-1903). Time was set according to Greenwich Mean Time (GMT) and for a long time it was called “London time”.

The first to switch to the use of “London time” (1840) was the Great Western Railway. Others began to imitate it, and by 1847 most British railways were using single time. On September 22, 1847, the Railway Clearing House, which set standards for the entire industry, recommended that Greenwich time be established at all stations with the permission of the Main Board. postal service. The transition took place on December 1, 1847.

On August 23, 1852, time signals were first transmitted by telegraph from the Royal Greenwich Observatory.

Until 1855, the vast majority of public clocks in Britain were set to Greenwich Mean Time. But the process of official transition to new system Timekeeping was constrained by British legislation, thanks to which local time remained officially accepted for many years. This led, for example, to such oddities as, for example, polling stations opening at 08:13 and closing at 16:13. Officially, the transition to new time in Britain took place after the introduction of legislation on the determination of time on August 2, 1880.

New Zealand

New Zealand was the first country to officially adopt standard time throughout the country (November 2, 1868). The country is located 172° 30" longitude east of Greenwich and its time was 11 hours 30 minutes ahead of Greenwich Mean Time. This standard was known as New Zealand Mean Time.

North America

In America and Canada, standard time was introduced on November 18, 1883, also by railroads. By that time, determining the time was a local matter. Most cities used "solar time" and the standard by which time was set was often a well-known clock in each locality (for example, clocks in church bell towers or in jewelry store windows.

The first person in the United States to sense the growing need for standardization of time was amateur astronomer William Lambert, who in early 1809 submitted to Congress a recommendation for the establishment of time meridians in the country. But this recommendation was rejected, as was Charles Dowd's original proposal, submitted in 1870, which proposed the installation of four, the first of which would pass through Washington. In 1872, Dowd revised his proposal, changing the center of reference to Greenwich. It was this last proposal of his, almost unchanged, that was used by the railroads of the United States of America and Canada eleven years later.

On November 18, 1883, the American and Canadian Railways adjusted the clocks at all railway stations according to (forward or backward). The belts were named Eastern, Central, Mountain and Pacific.

Despite the adoption of standard time by major railroads in the United States and Canada, it was still many years before standard time became the norm. Everyday life. But the use of standard time began to spread rapidly, given its obvious practical benefits for communications and travel.

Within a year, 85% of all cities North America(about 200), whose population exceeded 10,000, were already using standard time. Only Detroit and Michigan stood out noticeably.

Detroit lived on local time until 1900, when the City Council decreed that clocks be set back twenty-eight minutes to Central Standard Time. Half the city complied and half refused. After considerable debate, the decree was lifted and the city returned to solar time. In 1905, Central Time was adopted by city vote. By city ordinance in 1915 and then by vote in 1916, Detroit switched to Eastern Standard Time (EST).

Standard time was introduced throughout the United States with the passage of the Standard Time Act in 1918. The US Congress approved the standards previously established by the railroads, and transferred responsibility for any subsequent changes to them to the Interstate Commerce Commission, the only federal transportation regulatory body at that time. In 1966, the authority to enact time-related legislation was transferred to the Congressional Department of Transportation.

The borders that exist today in the United States have been significantly changed compared to their original version, and such changes are still occurring today. The Department of Transportation processes all change requests and conducts rulemakings. In general, borders tend to shift westward. For example, at the eastern end, sunset may be replaced an hour later (clockwise) by moving to the adjacent time zone to the east. Thus, the boundaries of the time zone are locally shifted to the west. The reasons for this phenomenon are similar to the reasons for the introduction of “maternity” time in Russia (see Summer time). The accumulation of such changes leads to a long-term tendency for the belt boundaries to move westward. This is not uncontrollable, but is very undesirable as it entails late sunrise in such areas, especially in winter. According to American law, the main factor in deciding whether to change a time zone is “to facilitate business.” According to this criterion, proposed changes were both approved and rejected, but most of them were accepted.

Standard time is a system of counting time based on dividing the Earth's surface into 24 time zones, every 15° in longitude. Time within the same time zone is considered the same. In 1884, at the International Conference it was decided to apply this system. In accordance with the international agreement of 1883, the prime ("zero") meridian is considered to be the one that passes through the Greenwich Observatory in the suburbs of London. Local Greenwich Time (GMT), agreed to be called Universal Time or "World Time"

On the territory of Russia, since March 28, 2010, there are 9 time zones (before that there were 11 time zones). The Samara region and Udmurtia switched to Moscow time (second time zone). Kemerovo region. (Kuzbass) - to Omsk (MCK+3). Kamchatka Territory and Chukotka - to Magadanskoye (MSK+8). In these five subjects of the Federation, on March 28, 2010, the clock hands were not moved.

Two belts are being abolished - the third (Samara, MSK+1) and the eleventh (Kamchatka, MSK+9). There are 9 of them in total, and the maximum time range in our country is reduced from 10 to 9 hours.

In Russia, since March 2011, after the transition to summer time, the clock hands are no longer moved throughout the year.

In 2012, the advantages of permanent winter time over summer are being discussed again, at all levels, and therefore a transition (this fall) to permanent, year-round winter time is possible.

Stable time is better for health. In the autumn-spring off-season, the body does not have to particularly adjust its biorhythms. Technical services and transport workers now do not have to, as before, when changing the hands of the clock, reconfigure equipment and change schedules.

Time zone of Moscow, according to stable time: +4 (GMT + 4:00)

The boundaries of standard time are drawn taking into account physical and geographical features - according to big rivers, watersheds, as well as along interstate and administrative boundaries. States can change these boundaries within the country.

The international U T C system is used ( World time; it is designated UTC/GMT or, which is the same thing - UTC), as well as the difference between local and Moscow time - MSK. The plus sign means east, the minus sign means west of the starting point.

The transition to summer time (one hour forward) and winter time (one hour back) occurs in spring and autumn, respectively. This rule applies in the European Union, Egypt, Turkey, New Zealand... The dates and procedure for transfer may vary slightly in terms of timing. Most countries have abandoned the autumn-spring change of clock hands: Russia and Belarus (since 2011), Kazakhstan, Turkmenistan, Uzbekistan, Tajikistan, India, China, Japan, Singapore, Taiwan...

World time - UTC/GMT - the value of Greenwich Mean Time (G M T) is equal to "Universal Coordinated Time" (U T C) with an accuracy of one second - GMT=UTC). The name U T C, over time, will completely replace the term “Greenich time”

Rice. 2 Map - World time zones and their offsets from UTC/GMT (Greenwich Time)

Table - time zones of cities around the world (UTC/GMT), in the summer

An example of winter and summer time designation: EST / EDT (Eastern Standard / Daylight Time Zone).
If, somewhere, winter time is considered standard, then it can be abbreviated, for example: ET, CT, MT, PT

Table - time zones of cities and regions in Russia, since 2011.
Local time difference shown:
MSK+3 - with Moscow;
UTC+7 - with Coordinated Universal Time (UTC = GMT)

Note: MSK = MSD (Moscow Summer Time) all year round

Terms and Definitions

Switching to Daylight Saving (Summer) Time (DST - Daylight Saving (Summer) Time) - moving the clock hand forward one hour, which was done annually on the last Sunday of March in order to get an additional hour during daylight hours, to save electricity (for lighting, etc. ). The return to winter time was carried out recently. Sunday in October. These transitions affected the biorhythms of the human body, his well-being, and it took a week of adaptation to get used to it. Manipulation of clock hands - common reason workers and employees being late for work.

The prime (prime) meridian is the Greenwich meridian with a geographic longitude of 0°00"00", dividing the globe into the western and eastern hemispheres. Passes through the former Greenwich Observatory (in the suburbs of London)

GMT (Greenwich Mean Time) - "Greenwich Time"- on the Greenwich meridian. Determined by astronomical observations daily movement of stars. It is unstable (within a second per year) and depends on the constant change in the speed of rotation of the Earth, the movement of geographic poles along its surface and the nutation of the planet’s rotation axis. Greenwich (astronomical) time is close in meaning to UTC (atomic time), and will still be used as its synonym. Another name is "Zulu Time"

In Russian-language meteorology, GMT is designated as SGV (Greenwich Mean / or Geographical / Time)

GMT= UTC (accurate to 1 second)

Time zone (Standard Time Zone) - difference with World Time UTC/GMT (example: UTC/GMT+4 - fourth time zone, east of Greenwich)

H:mm:ss - 24-hour format (example: 14:25:05). Minutes and seconds - with leading zeros

h:mm:ss - 12-hour format (example: 02:25:05 PM - "two and a half hours in the afternoon" - 14:25:05). Minutes and seconds - with leading zeros

AM - designation of time before noon in a 12-hour format (short version - "A")
PM - designation of time after noon in a 12-hour format

Universal Time UT (Universal Time) is the average solar time at the Greenwich meridian, determined from astronomical observations of the daily movements of stars. Its refined values ​​are UT0, UT1, UT2

UT0 - time at the instantaneous Greenwich meridian, determined from the instantaneous position of the Earth's poles

UT1 - time at the Greenwich mean meridian, corrected for the movement of the earth's poles

UT2 - time, taking into account changes in the speed of rotation of the Earth

TAI - time according to atomic clocks (International Atomic Time, since 1972). Stable, reference, never translated. Time and frequency standard

Time in the GPS navigation system has been in effect since January 1980. No amendments are introduced to it. It is ahead of UTC time by one and a half dozen seconds.

UTC (from English Universal Time Coordinated)- Coordinated Universal Time for the coordinated distribution of standard frequencies and time signals over radio, television and the Internet - "World Time". Its synonym: "Universal time zone"

The UTC time scale has been introduced since 1964 to harmonize the values ​​of UT1 (astronomical measurements) and TAI (atomic clocks).

Unlike Greenwich Mean Time, UTC is set using atomic clocks.

The speed of rotation of the earth is slowing down, and therefore, corrections are introduced into the UTC scale regularly, after a year or two or three, on June 30 or December 31 (leap seconds - “Coordination Second”), so that U T C is no more than a second ( more precisely, 0.9 s) differed from astronomical time (determined by the movement of the Sun), as UT1 lagged behind by a second. This international rule was adopted in 1972.

Time ratio in 2009: UTC (universal) lags behind TAI (atomic) - by 35s. Time in the GPS navigation system is 15 seconds ahead of UTC (counting since 1980, the difference is increasing) T glonass = Tutc + 3 hours (corrected, so the discrepancy between them does not exceed 1 ms.)

Precise time signals (for clock synchronization) are transmitted via radio channels, television, and the Internet - in the UTC system. More precisely, you can place it, for example, on the Mayak radio signal, but only on the long-wave or medium-wave range (on the “ground-surface wave”). On VHF/FM radio, the signal may be delayed up to several seconds from the true one.

In watches with automatic synchronization (English Radio controlled), time correction occurs from base stations, on ultra-long waves. This system was developed in Europe.

Exact local time service numbers in Russian cities 100 - Moscow Voronezh Cheboksary Chelyabinsk 060 - Bryansk Kaliningrad Krasnodar Murmansk St. Petersburg Samara Mobile operators do not have such a service, since a mobile phone is not limited geographically and can work not only in a specific city, but also in roaming .

UTC time is not converted neither in winter nor in summer, therefore, for those places where there is a conversion to summer time, the offset relative to UTC changes (in Moscow, before the abolition of winter time in 2011, the difference was: in winter - UTC+3, in summer - UTC+4).

Standard name abbreviations calendar months and days of the week in English (used in RSS and others): January February March April May June July August September October November December Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Monday Tuesday Wednesday Thursday Friday Saturday Sunday Mon Tue Wed Thu Fri Sat Sun

GMT - Greenwich Mean Time (or Geographical) Time (English Greenwich Mean Time, GMT) - the time of the meridian passing through the old Greenwich Observatory, near London. Used to indicate time on weather maps. Synonyms for GMT are GMT and UTC.

______________________________________________

Literature

“Time and calendar” - M.: Nauka. 1989

Global (satellite) navigation systems GLONASS (Russia), GPS (USA), Galileo (European Union) - make it possible to determine, using navigators, including portable ones, the current location (coordinates), trajectory and speed of movement of objects in any point on our planet and in the near-Earth outer space.

Depending on the method of operation and purpose, satellite GPS (Global Positioning System) navigators can be used for automobiles (car navigators), portable, marine, etc. The most common imported ones are Garmin, Mio, etc. There are completely autonomous configuration options - with batteries charging from solar panels or miniature thermoelectric generators (thermocouples). The navigation system is built into modern communicators, smartphones and Cell Phones, allowing you to obtain not only the geographic coordinates of the receiver’s location, but also the system time with an accuracy of a fraction of a microsecond.

Russian GLONASS has been operating since the mid-90s. The orbital constellation includes more than two dozen operating satellites. The system operates throughout Russia. Since 2009, transport, including passenger transport, has been massively equipped with this system.

Navigators are produced in Russia (Glospace SGK-70 and others) that can work simultaneously with several navigation systems - GLONASS, GPS, Galileo.

Glospace supports the SMILINK system (shows traffic jams) and can create detour routes. Signals can be received from several satellite systems at once.

Maps G P S - electronic maps for navigators and others mobile devices(communicators, PDAs/PDAs, smartphones, etc.) with GPS function.

• UTC: Time on the prime meridian is called Universal Coordinated Time. The discrepancy between the acronym was caused by the need for its universality for all languages.
• GMT: Previously, Greenwich Mean Time (GMT) was used instead of UTC, as the prime meridian was chosen to pass through the Royal Observatory Greenwich.
• Other time zones may be written as an offset from UTC. For example, Australian Eastern Standard Time (EST) is written as UTC+1000, meaning 10:00 UTC is 20:00 EST on the same day.
• Summer time does not affect UTC. It's just political decision time zone change (offset from UTC). For example, GMT is still in use: it is British national time in winter. In summer it becomes BST.
• Leap seconds: By international agreement, UTC is kept no more than 0.9 seconds from physical reality (UT1, which is measured in solar time) by introducing a "leap second" at the end of the last minute of the UTC year or the last minute of June.
• Leap seconds are not required to be declared (by astronomers) more than 6 months before their introduction. This poses a problem if you require any sort of second-by-second planning for more than 6 months.
• Unix time: measured by the number of seconds that have passed since the "epoch" (beginning of 1970 UTC). Unix time is not affected by time zones or daylight saving time.
• According to the POSIX.1 standard, Unix time is supposed to handle leap seconds by repeating the previous second, for example: 59.00 59.25 59.50 59.75 59.00 ← repeat 59.25 59.50 59.75 00.00 ← increment 00.25 This is a trade-off: you cannot express the leap second in any way in your system clock x and your time is guaranteed to go in the opposite direction. On the other hand, each day is exactly 86,400 seconds, and you don't need a table of all past and future leap seconds to convert Unix time into human-readable hours-minutes-seconds form.
• ntpd is supposed to retry after receiving "leap bits" from upstream time servers, but I've also seen it do nothing: the system jumps one second into the future, then slowly slides back to the correct time.

What every programmer should know about time

• Time zones are at the presentation level
  Most of your code should not deal with time zones or local time, it should report Unix time as it is.
• When you measure time, measure Unix time. This is UTC. It is easy to obtain (by system functions). It has no time zones or daylight saving time (or leap seconds).
• When storing time, store Unix time. This is one number.
• If you want to save human readable time (for example in logs), try to save it together with Unix time, not instead of.
• When displaying the time, always include the time zone offset. A time format without an offset is useless.
• The system clock is not accurate.
• You are online? Each different machine's system clock is not accurate in the same way.
• The system clock can, and will, jump forward and backward in time due to things outside of your control. Your program must be designed to survive this.
• Seconds ratio system clock to quantity real seconds - not exact and may vary. It mainly depends on the temperature.
• Don't blindly use gettimeofday() . If you need a monotonic (ever increasing) clock, look at clock_gettime() . [Java Option: Use System.nanoTime() instead of System.currentTimeMillis()]
• ntpd can change the system time in two ways:
  • Step: The clock jumps forward or backward to the correct time immediately
  • Twisting: Changing the frequency of the system clock so that it slowly moves toward the correct time.
  Twisting is preferred because it is less disruptive but is only useful for correcting small differences.

Special cases

• Time passes at the rate of one second per second for all observers. The frequency of the distant clock relative to the observer depends on speed and gravity. The clocks inside GPS satellites are adjusted to overcome the effects of relativity.
• MySQL stores columns of type DATETIME as number-packed values ​​"YYYYMMDD HHMMSS". If you are concerned about storing timestamps, store them as an integer and use the UNIX_TIMESTAMP() and FROM_UNIXTIME() functions to convert.