The Importance of Greenwich Mean Time
Greenwich Mean Time (GMT) is known as an international time standard and was formally established by the Washington Meridian Conference of 1884. The time is located in Greenwich, England, and marks the time of day that the Sun crosses the Prime Meridian. It is also calculated according to the rotation of the Earth, and the position of the Earth relative to the Sun.
When the Conference established GMT it wanted to establish a universal standard for time everywhere in the world, and that happened. Today that system is still used, although the system of UTC, Coordinated Universal Time is more accurate by leap seconds. Those leap seconds are calculated using caesium atomic clocks that came into play in the world of time by 1955.
Here, the time is calculated using the vibration of caesium clocks, a method much more accurate than assessing the Sun’s power and location at any given time of day in any country.
How Coordinated Universal Time (UTC) Works
Coordinated Universal Time or UTC time is almost the same thing as GMT but it is different by leap seconds. It is calculated using caesium atomic clocks that have been in existence since 1955. UTC has not, however, and has only been in place since 1972.
The caesium clocks use caesium atoms to measure time, and there are many all over the world. It is estimated that there are 70 in the United States. As technology advanced, this time became preferred because it measures time independent of the Earth’s placement to the Sun. Prior to that, the few seconds that GMT was off in time did not matter. When technology began to change the world, it did.
While GMT and UTC are used interchangeably, they do vary by leap seconds and UTC is preferred. In some cases, the synchronization of the Earth to GMT can be off by 33 seconds, which will make the difference in datelines and timestamps in many countries across the world. That happens all the time.
The leap seconds add up and become leap years, every four years.
GMT +8 Countries
Despite the preferred accuracy of UTC over GMT, GMT is still used. GMT 8 countries are countries whose time is calculated by adding 8 hours to GMT. The following countries are in GMT +8 time zone: