Gmt 2 time zone4/7/2024 Main article: History of longitude The Shepherd Gate Clock at the gates of the Royal Observatory, Greenwich is permanently kept on Greenwich Mean Time.Īs the United Kingdom developed into an advanced maritime nation, British mariners kept at least one chronometer on GMT to calculate their longitude from the Greenwich meridian, which was considered to have longitude zero degrees, by a convention adopted in the International Meridian Conference of 1884. The term GMT is especially used by United Kingdom bodies, such as the BBC World Service, the Royal Navy, and the Met Office and others particularly in Arab countries, such as the Middle East Broadcasting Centre and OSN. The term GMT should thus not be used for purposes that require precision. For navigation, it is considered equivalent to UT1 (the modern form of mean solar time at 0° longitude) but this meaning can differ from UTC by up to 0.9 s. Today, Universal Time usually refers to Coordinated Universal Time (UTC) or UT1 English speakers often use GMT as a synonym for UTC. To avoid confusion, the name Universal Time was introduced in 1928 to denote GMT as counted from midnight. Originally, astronomers considered a GMT day to start at noon, while for almost everyone else it started at midnight. Noon GMT is the annual average (the arithmetic mean) moment of this event, which accounts for the word "mean" in "Greenwich Mean Time". This event may occur up to 16 minutes before or after noon GMT, a discrepancy described by the equation of time. īecause 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. ![]() ![]() ![]() 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. 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. Greenwich Mean Time ( GMT) is the local mean time at the Royal Observatory in Greenwich, London, counted from midnight. If you are a frequent flyer or need to keep track of time somewhere else in the world, invest in a GMT watch and enjoy the convenience of viewing two time zones together.A The islands of Cape Verde are to the west of the African mainland.ī Mauritius and the Seychelles are to the east and north-east of Madagascar respectively. Such watches are produced by major watchmakers around the world including Rolex, Omega, Carl F. These watches cannot be labelled as GMT watches, though they are dual time zone watches and effectively show the time in different time zones. Some dual time zone watches feature an additional hour hand, despite not having the 24-hour scale. These watches must feature 24-hour scale by definition so as to avoid confusion between AM and PM in the second time zone. The GMT time or second time zone can be checked by looking at the additional hour hand and the regular minute hand. This additional hand can be set to any time zone in the world depending on the wearer’s requirement. One can define GMT as a watch that has an additional hour hand which points to 24-hour scale. Such timepieces are worn by those conducting business with people across the globe and need to know the time of that particular time zone. Dual Time Zone watches are a boon for frequent travellers who need to be aware of both their local time and home time. All the time, the pilot is kept informed about the home time on his watch. Since time zones are specified in terms of the difference with the GMT time, it is useful to be able to instantly check the current GMT time and thus quickly calculate the local time of the place. While in the air, pilots need to check the local time in the place they are flying through. ![]() GMT watches were initially introduced for pilots. So, if it is 7:00am in London, it is 8:00am in Madrid. For example, Madrid is in the time zone immediately after London and therefore is in the GMT +1 time zone. Other time zones are specified as their difference in hours from the Greenwich time, such as GMT +1 or GMT -1. Greenwich in London has the longitude of 0 degrees, thus making it the base point on the world time zone scale. The international time system divides the world into 24 time zones, and a place is assigned to a time zone based on its longitude. Many watches have ‘GMT’ written on the dial to indicate that they are dual time zone watches, and are called GMT watches. The second time zone is displayed using an additional hour hand. The definition of GMT means a watch that tells time in two time zones simultaneously.
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