• UTC: Time at the prime meridian is called Universal Coordinated Time. The mismatch of the acronym was caused by the need for its universality for all languages.
• GMT: Previously, Greenwich Mean Time (GMT) was used instead of UTC, since the prime meridian was chosen to pass through the Greenwich Royal Observatory.
• 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. This is just a political decision to change the time zone (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 convention, 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 they are introduced. This is a problem if you need any second-to-second planning for more than 6 months.
• Unix Time: Measured by the number of seconds 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 a leap second 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 compromise: you can't express a leap second in your system clock and your time is guaranteed to go backwards. 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-friendly hours-minutes-seconds.
• ntpd is supposed to retry after it receives "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 refer to presentation layer
  Most of your code should not be concerned with time zones or local time, it should be reporting Unix time as it is.
• When measuring time, measure Unix time. This is UTC. It's easy to get (by system functions). It has no time zones or daylight saving time (and leap seconds).
• When storing time, store Unix time. This is one number.
• If you want to save human-readable time (e.g. in logs), try to save it together with Unix time, not instead of.
• When displaying the time, always include the time zone offset. The time format without offset is useless.
• The system clock is not accurate.
• You are online? Every other machine's system clock is not accurate in different ways.
• The system clock can, and will, jump back and forth in time due to things that are out of your control. Your program must be designed to survive this.
• The ratio of the number of seconds system clock to quantity real seconds is not exact and may vary. It mainly depends on the temperature.
• Don't blindly use gettimeofday() . If you need a monotonic (constantly 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
  • Twist: Change the frequency of the system clock so that it moves slowly towards the correct time.
  Twisting is preferred because it is less destructive, but only useful for correcting a small difference.

Special occasions

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

Standard time is a system of counting hourly time, based on the division of 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 initial ("zero") meridian is the one that passes through the Greenwich Observatory in the suburbs of London. Local Greenwich Mean Time (GMT), agreed to be called universal or "World time" UTC/GMT/Z.

On the territory of Russia, since March 28, 2010 - 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 Omskoye (MCK+3). Kamchatka Territory and Chukotka - to Magadan (MSK + 8). In these five subjects of the Federation, on March 28, 2010, the clock hands were not translated.

Two belts are abolished - the third (Samara, MSC + 1) and the eleventh (Kamchatsky, MSC + 9). In total, there are 9 of them, and the maximum spread in time 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 be translated.

Moscow time zone, stable time: +4 (UTC/GMT + 4:00)

UTC (coordinated universal time) is the 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."
What is UTC time for?

UTC is used by international shortwave broadcasters in their frequency schedules and programming plans. Radio amateurs on the air, shortwave listeners, military, and service radio services also make extensive use of UTC. Greenwich Mean Time was based on the prime meridian that passes through Greenwich, England. GMT became the world time and date standard because it was used by the British Royal Navy and Merchant Navy during the nineteenth century. Today UTC is operated by precision atomic clocks, shortwave time signals and satellites to ensure the reliability and accuracy of the standard for scientific and navigational purposes. Despite refinements in accuracy, the UTC standard uses the same principles as GMT.
What time system does UTC use?

UTC uses the 24-hour system of time notation. "1:00 AM" in UTC is expressed as 0100 and declared "zero one hundred". Fifteen minutes past two are expressed as 0115; thirty-eight past two is 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.
What is the 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 made on Friday at 23:00 UTC in Moscow you will record on Saturday at 3:00 Moscow time. Conversely, if you made a QSO in Moscow on Monday 3:00 MT, the log should indicate “Sunday, 23:00 UTC.

The modern system of time zones is based on Coordinated Universal Time (UTC)(universal time), which determines the time of all time zones.

Local time in many countries of the Northern Hemisphere (but not in all) increases by 1 hour in summer (in the Southern Hemisphere it decreases by 1 hour at the same time), and returns to normal standard time in winter, which often also changes. Due to these seasonal and non-seasonal changes in local time in radio broadcasting, international transport, radio communications, e-mail and other international means of communication, there is a huge confusion about the docking of time between different countries.

UTC time is not translated in winter and summer, so for those places where there is a translation for summer time, the offset relative to UTC changes.

The initial (zero) meridian is the Greenwich meridian with geographic longitude equal to 0°00"00", which divides the globe into the western and eastern hemispheres. Passes through the former Greenwich Observatory (in the suburbs of London)

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

In Russian-speaking meteorology, GMT is denoted as GMT (Greenwich Mean / or Geographic / Time)

Unlike GMT, UTC is set using atomic clocks. The UTC time scale has been introduced since 1964 to harmonize UT1 (astronomical measurements) and TAI (atomic clocks).

Since 1900, the mean solar day has increased by 0.002 atomic seconds, and therefore Greenwich Mean Time diverges from international atomic time by about 1 second every 500 days. Taking into account this progressive phase shift between the two time scales, and without abandoning the high accuracy offered by atomic clocks, a compromise was reached in 1972 that led to the definition of the concept of Coordinated Universal Time (UTC), which is now used as the official measure of time in the world. . In essence, UTC time runs like international atomic time, and when the difference with Greenwich time reaches 1 second, 1 second is added to the UTC time scale, which is called jumping (leap second). Thus, the difference is always kept below 0.9 sec. The addition of the jump second is reported by the International Earth Rotation Service (IERS), which continuously monitors the rate of rotation. The best dates to add a jump second are June 30th and December 31st. By the way, the term UTC is also a compromise between the English CUT (Coordinated Universal Time) and the French TUC (Temps Universel Coordlnaire).

Coordinated Universal Time (UTC) always remains an independent reference for the whole world and from which, knowing the difference between your standard time, you can always calculate your local time.

Precise time signals are transmitted by radio, television, the Internet - in the UTC system.

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

Time Zones

Until the middle of the 19th century, time in different settlements with different longitudes was set chaotically, with a reference point at the time of sunrise and sunset. With the development of modern modes of transport (primarily railway) and the acceleration of the pace of transportation of goods, it became necessary to set time standards.

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

Due to the rotation of the Earth around its axis, the onset of a sunny day in different parts of the world is not the same. To correct for this astronomical phenomenon, a concept of time zones. To do this, the entire globe was conditionally divided into 24 time zones of 15 degrees, within which they agreed to consider the time as current in the same way. The Greenwich meridian was taken as zero. 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, which divides this zone in half. The moment of the upper climax of the Sun on this meridian falls approximately at 12-00, with an error of half an hour.

What is an administrative time zone?

However, geographic time zones are often not very convenient for administrative purposes. It is not surprising: the borders of states never pass 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, the Republic of Crimea adopted Moscow Time. And vice versa, after the collapse of the USSR, the young state of Ukraine, in order to move away from yesterday's "big brother", demonstratively moved the arrows closer to Europe.

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

The reforms of the 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 move 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 11 time zones to the people next year with the freezing of winter time. Because of this, it began to get dark early in a number of subjects.

In 2016, several subjects again changed their hourly "registration".

Thus, the whole world is divided into 24 time zones, but in each country, with one stroke of the 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 constant summer time was established in 2014) - no.

All this does not add order to chronological orientation and would lead to chaos at all 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 mean:

• Time, which is measured based on the observation of the position of the Moon, stars and other astronomical objects (abbreviated as UT0);
• UT1- time on the Greenwich meridian, corrected for the rotation of the Earth relative to the active nuclei of galaxies;
• UT1R- revised version of the previous formula, only adjusted for the effect of tides on the planet's turnover rate;
• UT2R- an improved version of the above time, with the clarification of various seasonal changes, the movement of lithospheric plates, etc., despite the fact that it is highly accurate, it is not used almost anywhere.
• UTC- has the UT1 formula in its base, but adjusted for international atomic time.

Usually, UTC is the last time listed as 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?

The atomic clock is considered the most accurate chronometer today. The error given by them is so small that it needs to be corrected approximately once every several tens of millions of years. Their work, as the name clearly implies, is based on effects occurring at the atomic level. It is atomic clocks that are used as the most accurate guide by accurate time services around the world.

There is nothing surprising in the fact that, based on the readings of this chronometer, the so-called International Atomic Time (AT) was introduced. Its accuracy is provided 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 - UTC, it is based on both atomic time and UT1. The latter standard has not found wide application due to its discontinuity. Once a year, the so-called leap 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 poles of the earth;
• In tachographs (a computer that is installed on a vehicle to track the state of the car and monitor the crew);
• In amateur radio.

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 used 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 sunny time. GMT was based on astronomical observations of the rotation of our planet relative to the heavenly bodies.

In domestic practice of navigation and geography, GMT is often referred to as SGW ( Geographic Mean Time/Greenwich Mean Time).

Currently, GBT 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 around the world. What's this? There is only one answer to this question, and that 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:

Standard time - a system of counting hourly time, based on the division of 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 initial ("zero") meridian is the one that passes through the Greenwich Observatory in the suburbs of London. Local Greenwich time (GMT), agreed to be called universal or "World time"

On the territory of Russia, since March 28, 2010 - 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 Magadan (MSK + 8). In these five subjects of the Federation, March 28, 2010 - the clock hands were not translated.

Two belts are abolished - the third (Samara, MSK + 1) and the eleventh (Kamchatsky, MSK + 9). In total, there are 9 of them, and the maximum spread in time 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 translated during the year.

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

Stable time is better for health. In the autumn-spring off-season, the body will not have to especially rebuild its biorhythms. Technical services and transport workers no longer have to, as before, when moving the hands of the clock, reconfigure equipment and change schedules.

Moscow time zone, stable time: +4 (GMT + 4:00)

Standard time boundaries are drawn taking into account physical and geographical features - along large rivers, watersheds, as well as along interstate and administrative borders. States can change these boundaries within the country.

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

The transition to summer time (one hour ahead) and winter time (one hour ago) is carried out in spring and autumn, respectively. This rule is valid in the European Union, Egypt, Turkey, New Zealand... Dates and order of transfer - may slightly differ in terms. Most countries have abandoned the autumn-spring shift of the clock: 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 will, over time, completely replace the term "Greenwich time"

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

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

Kamchatka	UTC/GMT+12
Magadan, Sakhalin.	UTC/GMT+12
Vladivostok	UTC/GMT+11
Yakutsk	UTC/GMT+10
Irkutsk	UTC/GMT+9
Krasnoyarsk	UTC/GMT+8
Omsk	UTC/GMT+7
Yekaterinburg	UTC/GMT+6
Moscow Moscow time, city of Sochi	UTC/GMT+4
Minsk "Eastern European Time" (EET)	UTC/GMT+3
Paris "Central European (Central European) Summer Time" (CEST - Central Europe Summer Time Zone)	UTC/GMT+2
London "Greenwich Time" / "Western European Time" (WET)	UTC/GMT+1
"Mid-Atlantic Time"	UTC/GMT-1
Argentina, Buenos Aires	UTC/GMT-2
Canada "Atlantic Time"	UTC/GMT-3
US - New York "Eastern Time" (EDT - US Eastern Daylight Time Zone)	UTC/GMT-4
Chicago (Chicago) "Central Time" (CDT - US Central Daylight Time)	UTC/GMT-5
Denver "Mountain Time" (MDT - US Mountain Daylight Time)	UTC/GMT-6
USA, Los Angeles, San Francisco "Pacific Time" (PDT - Pacific Daylight Time)	UTC/GMT-7

An example of the designation of winter and summer time: 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.
The local time difference is shown:
MSK + 3 - with Moscow;
UTC+7 - with Coordinated Universal Time (UTC = GMT)

Name winter / summer		Bias relatively Moscow time	Offset from UTC (world time)
USZ1	Kaliningrad time - the first time zone	MSK-1	UTC+3:00
MSK/MSD MSST/MSDT	Moscow time	MSK	UTC+4:00
SAMT/SAMST	Samara	MSK	UTC+H:00
YEKT / YEKST	Yekaterinburg time	MSK+2	UTC+6:00
OMST/OMST	Omsk time	MSK+3	UTC+7:00
NOVT/NOVST	Novosibirsk, Novokuznetsk Kemerovo, Tomsk. Barnaul	MSK+3	UTC+7:00
KRAT / KRAST	Krasnoyarsk time Krasnoyarsk, Norilsk	MSC+4	UTC+8:00
IRKT / IRKST	Irkutsk time	MSK+5	UTC+9:00
YAKT / YAKST	Yakut time	MSK+6	UTC+10:00
VLAT/VLAST	Vladivostok time	MSK+7	UTC+11:00
MAGT / MAGST	Magadan time Magadan	MSK+8	UTC+12:00
PETT / PETST	Petropavlovsk-Kamchatsky	MSK+8	UTC+I2:00

Note: MSK = MSD (Moscow Summer Time) throughout the year

Terms and Definitions

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

The initial (zero) meridian is the Greenwich meridian with geographic longitude equal to 0°00"00", which divides the globe into the western and eastern hemispheres. Passes through the former Greenwich Observatory (in the suburbs of London)

GMT (Greenwich Mean Time) - "Greenwich Mean Time" on the Greenwich meridian. It is determined by astronomical observations of the daily movement of stars. It is unstable (within a second per year) and depends on the constant change in the speed of the Earth's rotation, the movement of the geographic poles on its surface and the nutation of the planet's axis of rotation. Greenwich (astronomical) time is close in value to UTC (atomic time), and for the time being will be used as its synonym. Also called "Zulu Time"

In Russian-speaking meteorology, GMT is denoted as GMT (Greenwich Mean / or Geographic / Time)

GMT= UTC (accurate to 1 second)

Time zone (Standard time zone) - difference from UTC / GMT World Time (example: UTC / GMT + 4 - the 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 12-hour format (abbreviated version - "A")
PM - designation of time after noon in 12-hour format

Universal Time UT (Universal Time - Universal Time) - the mean solar time on the Greenwich meridian, is determined by astronomical observations of the daily movements of stars. Its updated values ​​are UT0, UT1, UT2

UT0 - time on the instantaneous Greenwich meridian, determined by the instantaneous position of the Earth's poles

UT1 - time on 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 - atomic clock time (International Atomic Time, since 1972). Stable, reference, never translated. Time and frequency standard

The time in the GPS navigation system has been valid since January 1980. It does not include amendments. It is ahead of the UTC time by 15 seconds.

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

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

Unlike GMT, UTC is set using atomic clocks.

The speed of rotation of the earth is slowing down, in connection with which the UTC scale is regularly, after a year or two or three, on June 30 or December 31, amendments are introduced (leap seconds - "Second of coordination"), 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.

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

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

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

Numbers of exact local time services in Russian cities 100 - Moscow Voronezh Cheboksary Chelyabinsk 060 - Bryansk Kaliningrad Krasnodar Murmansk St. Petersburg Samara Cellular operators do not have such a service, since the mobile phone is not limited geographically and can work not only in a certain city, but also in roaming .

UTC time is not translated either in winter or summer, therefore, for those places where there is a transfer 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 abbreviations for the names of 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 (GMT) - the time of the meridian passing through the old Greenwich Observatory near London. It is used as a designation of time on weather charts. Synonyms for GMT are GMT and UTC.

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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 objects in any point of our planet and in near-Earth outer space.

According to the method of operation and purpose, satellite GPS (Global Positioning System) navigators are automobile (car navigators), portable, marine, etc. The most common imported ones are Garmin, Mio, etc. There are completely autonomous configuration options - with charging batteries from solar panels or miniature thermoelectric generators (thermocouples). The navigation system is built into modern communicators, smartphones and cell phones, allowing you to receive not only the geographic coordinates of the receiver's location, but also the system time with an accuracy of fractions of a microsecond.

The Russian GLONASS (Glonass) has been operating since the mid-1990s. The orbital constellation includes more than two dozen active satellites. The system operates throughout Russia. Since 2009, transport, including passenger vehicles, 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 is able to lay detour routes. Signals can be received from several satellite systems at once.

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