Question

What is IST? What is its importance?

Answer 1

IST is Indian Standard Time.

• By an international agreement, the Prime Meridian is the meridian of longitude passing through the Greenwich observatory (near London).
• The value of 0° has been assigned to Prime Meridian.
• Indian Standard Time is ahead of Greenwich Mean Time by 5 hours and 30 minutes.
• The standard meridian in multiples of 7°30′ of longitude was selected as per general understanding among all the countries of the world.
• 82°30′ E is selected as the ‘standard meridian’ of India.
• In every four minutes of time, the sun traverses 15 degrees of longitude per hour or one degree of longitude.
• There are some countries like the USA, Russia which have more than one standard meridian due to their vast west-to-east extent.

What is the use of the standard Meridian?

• The Standard Meridian is the time at the central meridian of the country and its local time is taken as the standard time for the whole country.
• This is done to maintain uniformity of time within the territorial limits of a country to the maximum possible extent.
• There is a time lag of two hours, as we move from Gujarat to Arunachal Pradesh.
• Hence, the standard time for the whole country is the time along the Standard Meridian of India (82°30’E) which passes through Mirzapur. Mirzapur is located in Uttar Pradesh.
• To determine the local time of an area with respect to the time at the Prime Meridian (0°Longitude), we use the rate of the time at which the sun traverses over certain degrees of longitudes.

Further Reading

1. Name the five states through which the Indian Standard Meridian passes.
2. Why do we need a standard meridian for India?
3. What is the difference between Latitude and Longitude?