Why is gmt in greenwich

However, some individuals still use the term Greenwich Mean Time since it represents civil time in Britain. Though UTC is currently used right now as the reference for other time zones, it is still essential to understand how GMT became the international standard before.

Greenwich Meridian was recommended as the Prime Meridian of the World in This is because the United States had already chosen Greenwich as the basis for its national time zone system.

Greenwich Mean Time refers to the yearly average mean of the time each day when the sun crosses the Prime Meridian. The clock was changed in the 20th century to indicate Greenwich Mean Time, in which the counting of the 24 hours of each day starts at midnight.

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As the reference for GMT Greenwich Mean Time , the Prime Meridian at Greenwich became the centre of world time and the basis for the global system of time zones in Buy Now. A stylish hour analogue clock that will make a statement on any wall, with its bold monochrome face, and matte black metal casing How old is Earth? How fast can you think? How long is a light year and how short is a femtosecond?

What does Greenwich Mean Time mean? A meridian is a north-south line, selected as the zero reference line for astronomical observations. By comparing thousands of observations taken from the same meridian it's possible to build up an accurate map of the sky. There were two main reasons for the choice.

The first was the fact that the USA had already chosen Greenwich as the basis for its own national time zone system. Therefore the Prime Meridian at Greenwich became the centre of world time.

Every place on Earth was measured in terms of its distance east or west from this line. The line itself divided the eastern and western hemispheres of the Earth - just as the Equator divides the northern and southern hemispheres.

If you stand with one foot on one side and the other on the left, you are perfectly in the middle of east and west, according to the prime meridian line. Before this, almost every town in the world kept its own local time. There were no national or international conventions which set how time should be measured, or when the day would begin and end, or what length an hour might be.

When the railway and communications networks expanded in the s and s, there needed to be an international time standard. By the s most countries had adopted hourly time zones, but in some instances these differed within regions because of geography, distance or politics. This remains the case today, with a number of countries carrying different time zones between states. Some countries including China use a single time zone despite spanning more than 15 degrees of longitude.