Until now, in Windows computer settings, the time zone is specified by the abbreviation GMT. What is this and how does it relate to the modern UTC time coordination system? We will talk about this in our article. not everyone can do it at their location relative to Greenwich. But we will try to explain this issue in popular language. First of all, you need to answer the question: “What is GMT?” How does this abbreviation stand for?

British snobbery

In the old days, time was set at noon. When the sun was at its zenith, that is, it reached its highest point in the visible sky, it was believed that it was twelve o'clock in the day. With the development of international trade, the need arose to coordinate time into a single system. The starting point was He passes through the Royal Observatory in the town of Greenwich, near London.

Thus, the abbreviation GMT stands for Greenwich Mean Time. All the territories that are to the west of Greenwich are behind his time, and those that are located to the east are ahead of him. There is another significant meridian on the surface of planet Earth. This Territory, located to the east of it, lives (in the truest sense of the word) yesterday. In 1972, the new abbreviation UTC replaced GMT. What time is this? The abbreviation stands for Coordinated Universal Time.

Time Zones

In Russian-language metrology, the abbreviation SGV is used instead of GMT. What is it? The letters stand for “Mean Geographic Time.” But again, we can’t escape Greenwich. After all, the whole world counts its clock from the prime meridian. If you are to be punctual and accurately determine the time for each point on the globe, you need to know its distance from Greenwich to the west or east. And Coordinated Universal Time (in other words, UTC) basically displays noon in certain countries (or parts thereof). If GMT is a time that does not know political boundaries, then time zones often extend to an entire state (if it does not extend very far from west to east). Thus, UTC+0 is the time not in and on the prime meridian, but throughout Great Britain and Ireland, as well as Iceland, Portugal, Morocco, etc. But the calculation of hours using the UTS system is carried out on the same principle as in GMT .

Summer and winter time

In countries at high latitudes, the length of daylight varies greatly depending on the time of year. Therefore, northern countries often switch to summer time. Residents of these countries move their clocks forward an hour. This happens on the last Sunday of March. The UK is also on the list of countries that practice summer clocks. But true noon from April to October is then observed at 1 pm, because Greenwich Mean Time does not depend on the season.

Countries lying near the equator, where at any time of the year there is approximately twelve hours, do not move the hands seasonally. They constantly live according to winter (true) time. On this basis, the Russian Federation decided not to move the hands forward an hour every year. By the way, another country located at high latitudes refused to switch to summer time. This is Iceland. The island nation operates according to Greenwich Mean Time (GMT+0). Great Britain and Ireland, which lie on approximately the same meridian, are at UTC+0 in winter and UTC+1 in summer.

What are UTC and GMT for?

Time is a concept that loves precision. For coordinated actions, dispatch services located at points of the Earth remote from each other need to know what hours, minutes and seconds it is. Radio broadcasters of different frequencies also need coordinated time. UTC is necessary to establish a certain standard for navigational and scientific purposes. Throughout the nineteenth century, sailors of the British fleet, sailing the world's oceans, calculated time using GMT. Moving west of Greenwich, they took away hours, and moving east, they added hours. According to this principle, it is now divided into time zones. For example, Vladivostochnaya 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 territories adjacent to the Atlantic Ocean of the USA and Canada, and also in Jamaica, Panama, Haiti, Bahamas) - GMT-5.

Instructions

Determine your time zone offset relative to the Greenwich meridian. You can find it out, for example, from the system time settings in your operating system. Click the clock in the notification area of ​​the taskbar with the left mouse button, and an additional panel with a calendar and an analog clock will pop up on the screen. At the bottom of it there is a link “Change date and time settings” - click on it. The system will open an additional settings window with three tabs, one of which is “Date” and has a “Time Zone” section. In this section you will see the shift of your local time relative to the Greenwich meridian - the corresponding inscription could, for example, be like this: “UTC +04:00 Volgograd, Moscow, St. Petersburg.” This means that your operating system's system clock is shifted forward by four hours relative to time zone zero.

Subtract the time offset set for your time zone from the current time to determine the corresponding Greenwich Mean Time. For example, if your clock shows 26 minutes past nine in the morning, and the time zone corresponds to the time, then this offset is equal to four hours, and it is now 26 minutes past five in GMT.

Use services to determine Greenwich Time if you have Internet access. This is an even simpler way. For example, you can follow the link http://time100.ru/gmt.html and you will see the current Greenwich time immediately, without additional calculations.

Use the built-in functions of the programming language if you need to determine Greenwich Time programmatically - they are provided in most scripting languages. Most often, such functions refer to UTC time, and this is reflected in their names. For example, in PHP these are the gmdate and gmmktime functions, in the JavaScript language - a whole range of functions (getUTCDate, getUTCDay, getUTCMilliseconds and others), in the MQL5 language - TimeGMT, etc.

Sources:

• GMT

Due to the fact that the size of our planet is enormous, at the same period of time, different points of the Earth have their own local solar time. And in order to avoid confusion in clarifying the question: “So what time is it?”, the standard time system was adopted. And the Earth was conditionally divided into 24 sentinels belts. The reference point was taken as the zero meridian, from which they go east sentinels belts+1, +2, +3, etc., and to the west: -1, -2, -3, etc. So, thanks to the time zone system, it is now quite easy to determine what you are looking for.

You will need

• - computer
• - time zone map
• - world map showing degrees of longitude

Instructions

Turn it on and click on the clock indicator in the lower right corner of the screen. Now, in the window that opens, click on the “Change date and time settings” function. And, in a new window, select the “Change time zone” function. You will see a long list of cities that belong to them. Of course, only capital cities are listed here and no small towns. So, if you want to find out the time zone of a small city, just find the capital of its country in this list, since, usually, there is one time zone within one country.

Use an ordinary world map, which shows in detail the middle meridians: 0°, 15°, 30°, 45°, 60°, etc. The fact is that one time zone occupies approximately 15°, but not clearly from 0° to 15°, from 15° to 30°, from 30° to 45°, etc., but with an offset that is equal to - 7 °30. And, in order to determine the boundaries, for example, of a sentry belts UTC+1, you need to draw to the right and left of the middle meridian of 15° east longitude at a distance of 7°30". In order to determine the time zone of a place that is located, for example, in the area of ​​60° west longitude, you need to calculate its position according to in relation to the prime meridian: 15° - one, 30° - two, 45° - three, 60° - four. So 60° west longitude is the UTC-1 time zone.

Use a detailed map of time zones. This is the simplest and most reliable way to determine the time zone of a particular point on the globe. Since here, not only the boundaries of each of the 24 time zones are indicated, but there is also a note - whether it changes over time. It looks, for example, like this: +1(+2), and that the country belongs to the UTC+1 time zone, but in summer, it belongs to the UTC+2 time zone. Of course, do not forget to take into account that different hemispheres have summer and winter at different times. Another big plus of such a map is the ability to determine whether different sentinels belts, as in Russia, or, despite the large territory, only one belt is adopted, as in China.

note

Despite the generally accepted system of time zones, in reality, in order to maintain a uniform time within one country or administrative unit, the boundaries of zones are shifted, so in some places some time zones are superseded by neighboring ones.

Helpful advice

When determining your time zone, do not forget that in some countries local time differs from universal time not only by a standard hour, but also by an additional 30 or 45 minutes.

When trying to find out how much in another region and in another country, you will most likely encounter the concept “ hourly belt" But it is often denoted by the special abbreviation GMT. Where did it come from, and what does it mean?

GMT is the English phrase Greenwich Mean Time, which is like "Greenwich Mean Time". Mean time refers to the astronomical time of the meridian on which the Greenwich Observatory was previously located. This place is considered the “reference point” for all sentries belt It was not by chance that the Greenwich Royal Observatory became the place where time was counted. It appeared back in the 17th century in Greenwich (England). Calculations important for seafarers were carried out there, including those relating to time. When Great Britain became the largest empire, Greenwich time calculation spread to its dependent states, and at the end of the 19th century, almost the whole world adopted this reporting system. In 1884, even a special international conference was held to determine the “meridian of reference.” Time in other countries was determined by distance from the Greenwich meridian, that is, from that clock belt and, where Great Britain was located. In the seventies, the time system was replaced by a more accurate one - by calculation according to universal coordinated time, slightly different from the time on the Greenwich meridian. However, the abbreviation GMT is still often used as a tribute to tradition. What do the numbers in front of the GMT abbreviation mean? This is in Greenwich Observatory and other selected area. For example, if you are at a sentry belt e GMT+3, for example, in Moscow, the time difference with the reference meridian is three hours, while in Moscow the time is later. The minus sign in front of the number indicates that time should be counted in the opposite direction: when it is 11 o’clock in London, then in the region with GMT-2 it is still 9. But we must not forget that not all countries have clocks for winter time. In 2011, it was also canceled in Russia. In this case, GMT will vary depending on the season.

The emergence of time zones on our planet was due to the banal convenience of communication and the division of different countries and cities in accordance with the real time of day. Scientists have divided the entire surface of the Earth into 24 time zones, taking into account a gap of 15 degrees of longitude. Time that is within the same time zone is considered the same.

Instructions

The decision to use time zones was made at the International Conference in 1884. The meridian passing through the Greenwich Observatory near London began to be considered the year's time reference point. It was this observatory that became the unifying link. It was originally built by order of King Charles II for sailors.

Instant.now() // Capture the current moment in UTC.

Generate a string to represent this value:

Instant.now().toString()

2016-09-13T23:30:52.123Z

details

In Java 8, the current moment is captured only with a resolution of up to milliseconds. Java 9 has a fresh implementation of Clock that captures the current moment up to the full nanosecond capability of this class, depending on the clock hardware capabilities of your host computer.

Its toString method generates a string representation of its value using one specific ISO 8601 format. This format outputs zero, three, six, or nine digits (milliseconds, microseconds, or nanoseconds) as needed to represent a fraction of a second.

If you want more flexible formatting or other advanced features, then apply a zero offset from UTC to UTC itself (the ZoneOffset.UTC constant) to get the OffsetDateTime .

OffsetDateTime now = OffsetDateTime.now(ZoneOffset.UTC);

Dump to console...

System.out.println("now: " + now);

When you run...

Now: 2014-01-21T23:42:03.522Z

DateTimeZone zoneMontréal = DateTimeZone.forID("America/Montreal"); DateTime now = DateTime.now(zoneMontréal);

DateTime now = DateTime.now(DateTimeZone.UTC);

If you really want to use the JVM's current default time zone, make an explicit call so that your code is self-documenting.

DateTimeZone zoneDefault = DateTimeZone.getDefault();

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 no longer 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 zone time are drawn taking into account physical and geographical features - along large rivers, watersheds, as well as along interstate and administrative boundaries. States can change these boundaries within the country.

The international system U T C (World Time is used; 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

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
Ekaterinburg	UTC/GMT+6
Moscow Moscow time, Sochi city	UTC/GMT+4
Minsk "Eastern European Time" (EET)	UTC/GMT+3
Paris "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
USA - 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 (MDT - US Mountain Daylight Time)	UTC/GMT-6
USA, Los Angeles, San Francisco "Pacific Daylight Time" (PDT - Pacific Daylight Time)	UTC/GMT-7

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)

Name winter / summer		Bias relatively Moscow time	Offset relative to 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 / OMSST	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	MSK+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) 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 is a common reason why workers and employees are 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 from astronomical observations of the daily motion 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 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 (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 near-Earth 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 receive 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.

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