Question

Write a note on GMT and IST.

Answer 1

Hint: The earth's surface is divided into 24 time zones of one hour each. Each zone thus covers 15 degrees of longitude.

Complete Step by Step Answer: In countries with a large east-west extent, the variation in local time is very great. In India, there is a difference in the local times of Dwarka in Gujarat and Dibrugarh in Assam The difference between these two states is 1 hour and 45 minutes. So because of this reason, it is important to adopt the local time of some central meridian of a country as the standard time for the country.

In India, the longitude of 82.5 degrees East is treated as the standard meridian. So, for the whole country, the local time at this meridian is taken as the standard time and is known as the Indian Standard Time (IST).

The Greenwich Mean Time (GMT) refers to the time at the Prime Meridian. This is the standard time for the United Kingdom. Often, the standard times in different countries are expressed as a difference in the number of hours from Greenwich Mean Time. The Indian Standard Time is 5.5 hours ahead of the GMT. This means that when it is 1 P.M. in the United Kingdom it is 6:30 P.M. in India.

Some countries have adopted more than one standard time as they have a great longitudinal extent. For example, in the United States of America, there are four standard times, in Russia there eleven and in China, there are five.

Note: The places along Prime Meridian will have noon or midday when this Meridian of Greenwich has the sun at the highest peak in the sky. As the earth rotates from west to east, those places lying to the west of Greenwich will be behind Greenwich time and those to the east will be ahead of it.