Azerbaijan Time in the context of Gulf Standard Time

Greenwich Mean Time (GMT) is the local mean time at the Royal Observatory in Greenwich, London, counted from midnight. At different times in the past, it has been calculated in different ways, including being calculated from noon; as a consequence, it cannot be used to specify a particular time unless a context is given. The term "GMT" is also used as one of the names for the time zone UTC+00:00 and, in UK law, is the basis for civil time in the United Kingdom.

Because of Earth's uneven angular velocity in its elliptical orbit and its axial tilt, noon (12:00:00) GMT is rarely the exact moment the Sun crosses the Greenwich Meridian and reaches its highest point in the sky there. This event may occur up to 16 minutes before or after noon GMT, a discrepancy described by the equation of time. Noon GMT is the annual average (the arithmetic mean) moment of this event, which accounts for the word "mean" in "Greenwich Mean Time".

Kaliningrad Time (KALT; Russian: калининградское время, romanized: kaliningradskoye vremya) is the time zone two hours ahead of UTC (UTC+02:00) and one hour behind Moscow Time (MSK−1). It is used in Kaliningrad Oblast.

Until 2011, Kaliningrad Time was identical to Eastern European Time (UTC+02:00; UTC+03:00 with daylight saving time). On 27 March 2011, Russia moved to permanent DST, switching Kaliningrad time permanently to UTC+03:00. On 26 October 2014, this law was reversed but daylight saving time was not reintroduced, so Kaliningrad is now permanently set to UTC+02:00.

Central European Summer Time (CEST, UTC+02:00), sometimes referred to as Central European Daylight Time (CEDT), is the standard clock time observed during the period of summer daylight-saving in those European countries which observe Central European Time (CET; UTC+01:00) during the other part of the year. It corresponds to UTC+02:00, which makes it the same as Eastern European Time, Central Africa Time, South African Standard Time, Egypt Standard Time and Kaliningrad Time in Russia.

Eastern European Time (EET) is one of the names of the UTC+02:00 time zone, 2 hours ahead of Coordinated Universal Time. The zone uses daylight saving time, so that it uses UTC+03:00 during the summer.

A number of African countries use UTC+02:00 all year long, where it is called Central Africa Time (CAT), although Egypt and Libya also use the term Eastern European Time.

Europe spans seven primary time zones (from UTC−01:00 to UTC+05:00), excluding summer time offsets (five of them can be seen on the map, with one further-western zone containing the Azores, and one further-eastern zone spanning the Ural regions of Russia and European part of Kazakhstan). Most European countries use summer time and harmonise their summer time adjustments; see Summer time in Europe for details.

The time zones actually in use in Europe differ significantly from uniform zoning based purely on longitude, as used for example under the nautical time system. The world could in theory be divided into 24 time zones, each spanning 15 degrees of longitude. However, due to geographical and cultural factors, it is not practical to divide the world so evenly, and actual time zones may differ significantly from those based purely on longitude. In Europe, the widespread use of Central European Time (CET) causes major variations in some areas from solar time. Based on solar time, CET would range from 7.5 to 22.5°E. However, for example Spain (almost entirely in the Western hemisphere) and France (almost entirely west of 7.5°E, as illustrated in the map below) should theoretically use UTC, as they did before the Second World War. The general result is a solar noon which is much later than clock noon, and later sunrises and sunsets than should theoretically happen. The Benelux countries should also theoretically use GMT.

Western European Time (WET, UTC+00:00) is a time zone covering parts of western Europe and consists of countries using UTC+00:00 (also known as Greenwich Mean Time, abbreviated GMT). It is one of the three standard time zones in the European Union along with Central European Time and Eastern European Time.

The following Western European countries and regions use UTC+00:00 in winter months:

Western European Summer Time (WEST, UTC+01:00) is a summer daylight saving time scheme, 1 hour ahead of Greenwich Mean Time and Coordinated Universal Time. It is used in:

• the Canary Islands
• Portugal (including Madeira but not the Azores, which uses UTC+00;00)
• the Faroe Islands

The following countries also use the same time zone for their daylight saving time but use a different title:

During British Summer Time (BST), civil time in the United Kingdom is advanced one hour forward of Greenwich Mean Time (GMT), in effect changing the time zone from UTC+00:00 to UTC+01:00, so that mornings have one hour less daylight, and evenings one hour more.

BST begins at 01:00 GMT every year on the last Sunday of March and ends at 02:00 BST on the last Sunday of October. The starting and finishing times of daylight saving were aligned across the European Union on 22 October 1995, and the UK retained this alignment after it left the EU; both BST and Central European Summer Time begin and end on the same Sundays at 02:00 Central European Time, 01:00 GMT. Between 1972 and 1995, the BST period was defined as "beginning at two o'clock, Greenwich mean time, in the morning of the day after the third Saturday in March or, if that day is Easter Day, the day after the second Saturday in March, and ending at two o'clock, Greenwich mean time, in the morning of the day after the fourth Saturday in October."

Ireland uses Irish Standard Time (IST, UTC+01:00; Irish: Am Caighdeánach Éireannach) in the summer months and Greenwich Mean Time (UTC+00:00; Irish: Meán-Am Greenwich) in the winter period.

The Standard Time Act 1968 legally established that "the time for general purposes in the State (to be known as standard time) shall be one hour in advance of Greenwich mean time throughout the year". This act was amended by the Standard Time (Amendment) Act 1971, which legally established Greenwich Mean Time as a winter time period. Ireland therefore operates one hour behind its statutory standard time during the winter period, and reverts to standard time in the summer months. This definition contrasts with the practice of other states in the European Union, which operate one hour ahead of their standard time during the summer period, but produces the same result. The net effect is that time in Ireland is the same as that in Portugal and the United Kingdom, as well as, during the winter months, Iceland.

Eastern European Summer Time (EEST) is one of the names of the UTC+03:00 time zone, which is 3 hours ahead of Coordinated Universal Time. It is used as a summer daylight saving time in some European and Middle Eastern countries, which makes it the same as Arabia Standard Time, East Africa Time, and Moscow Time. During the winter periods, Eastern European Time (UTC+02:00) is used.

Since 1996, European Summer Time has been applied from the last Sunday in March to the last Sunday in October. Previously, the rules were not uniform across the European Union.

In Turkey, time is given by UTC+03:00 year-round. This time is also called Turkey Time (TRT). The time at most is the same as in the Moscow Time and Arabia Standard Time zones. TRT was adopted by the Turkish Government on 8 September 2016. It was also in use in Northern Cyprus until it reverted to Eastern European Time (EET) in October 2017.

During some seasons (March–October), the TRT coincides with the Eastern European Summer Time (the daylight-saving version of the Eastern European Time). The IANA time zone identifier for Turkey is Europe/Istanbul.

Armenia Time (AMT) is a time zone used in Armenia. It is four hours ahead of UTC at UTC+04:00.

Clock time is about one hour later than solar noon in Armenia. Consequently, population activity hours are similar to those in Paris or Barcelona, which have about the same shift to solar time. They are about one hour later compared to those in Berlin and Vienna, and are two hours later than those in Warsaw and New York.

Georgia Time (GET) is a time zone used in Georgia and it is uniform throughout the country. It moved from zone UTC+04:00 to UTC+03:00 on 27 June 2004, then back to UTC+04:00 on 27 March 2005. Georgia has not observed daylight saving time since 2004.

The IANA time zone database contains one zone for Georgia in the file zone.tab, named after Georgian capital city, Tbilisi. In Georgia, it is called the Tbilisi Time (Georgian: თბილისის დრო, romanized: Tbilisis Dro).

Summer time in Europe is the variation of standard clock time that is applied in most European countries (apart from Iceland, Belarus, Turkey and Russia) in the period between spring and autumn, during which clocks are advanced by one hour from the time observed in the rest of the year, with a view to making the most efficient use of seasonal daylight. It corresponds to the notion and practice of daylight saving time (DST) to be found in some other parts of the world.

In all locations in Europe where summer time is observed (the EU, EFTA and associated countries), European Summer Time begins at 01:00 UTC/WET (02:00 CET, 03:00 EET) on the last Sunday in March (between 25 and 31 March) and ends at 01:00 UTC (02:00 WEST, 03:00 CEST, 04:00 EEST) on the last Sunday in October (between 25 and 31 October) each year; i.e. the change is made at the same absolute time across all time zones. European Union Directive 2000/84/EC makes the observance of summer time mandatory for EU member states (except overseas territories). A proposal to repeal this directive and require that member states observe their own choice year-round is currently going through the legislative process as of July 2020, but has not seen progress since October 2020.

UTC+03:00 is an identifier for a time offset from UTC of +03:00. In areas using this time offset, the time is three hours ahead of the Coordinated Universal Time (UTC).Following the ISO 8601 standard, a time with this offset would be written as, for example, 2019-02-08T23:36:06+03:00.