Full Form of GMT :
Greenwich Mean Time (or) Greenwich Meridian Time
GMT Full Form is Greenwich Meridian Time. It refers to the mean solar time in Greenwich, London. Greenwich in England has been the GMT home since 1884. It is also referred as Greenwich Mean Time. It is measured from Greenwich Meridian Line at the Royal Observatory located in Greenwich. In simple terms, it is the base place from which the time zones around the world are measured. The prime meridian here is the Longitude Zero Degrees. GMT is the average time taken by the earth to rotate on its axis in 24 hours. Greenwich, England is located in (1) Longitude 00 0’0” (2) Latitude 510 28’ 38”N (North of Equator)
It was previously applied as the standard for International Civil Time however, now it is no longer used, as it has been superseded by a much-sophisticated standard Coordinated Universal Time (abbreviated as UTC). In the contemporary context, particularly in the United Kingdom, the Greenwich Mean Time is regarded as equivalent to the UTC and for the purposes of navigation; it is regarded as equivalent to the UT1.
Even though Greenwich Mean Time, which will hereinafter be referred to as GMT throughout the article, is not in common use, it is still in use by several English bodies such as the Royal Navy, the BBC World Service, the MET department, as well as certain Arabian bodies such as the OSN and the Middle East Broadcasting Centre. It is a common term in commonwealth countries, including India. Let us find out other important aspects of GMT in the following paragraphs. So, here are three points about GMT you should know:
Use of GMT in legislation
As mentioned before, GMT is still widely used in the United Kingdom and it has found a place in various legislations. In fact, the civil time the United Kingdom uses is legally the GMT. As per the Interpretation Act 1978, it is mentioned as Greenwich mean time, without any capitalization. Section 9 of the same Act provides that whenever the term time is used in any legislation, it shall mean to be GMT unless of course otherwise has been expressly and clearly provided in the Act itself.
Similarly in subsection 23(3) of the same Act, this will be applicable to deeds, contracts, and other instruments. Despite the wide use of GMT in the United Kingdom, its use has been discouraged by many due to its imprecise nature. Apart from the United Kingdom, there are several countries that define local time in respect of the GMT. For example, in Ireland, Section 1 of the Standard Time (Amendment) Act 1971 provides for the same. Similarly in Canada, the Interpretation Act 1971 makes use of the expression “Greenwich time”.
History of GMT
GMT has been in use for many decades in the United Kingdom. The Greenwich Mean Time was adopted officially by the International Meridian Conference that was convened in the year 1884. With this, GMT became a worldwide standard and was extensively implemented in maritime situations. In the year 1847, GMT was adopted in Great Britain by the Railway Clearing House, following which many railway companies began adopting it. However, for many years the Local Mean Time remained the official time until in the year 1880, the GMT was legally adopted across Britain. Soon after, it spread to other nations and colonies of these nations.
Greenwich Mean Time was previously regarded by the astronomers to begin with noon, however, every other person would consider it to start at midnight. This caused a lot of confusion in the determination of time and therefore, Universal Time was introduced for denoting GMT counted from midnight, not noon. Today, this Universal Time is used in reference to UT1 or UTC.
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