Question

What is the difference between the time of sunrise in Arunachal Pradesh and Gujarat?

Answer 1

Hint: The position of the Sun does not determine the time on the watch. Note that time is determined not by sunrise/sunset, but by the time zone. Two time zones are available: the local time zone and the standard time zone.

Complete solution:
The 82°30' Eastern Longitude has been taken as the standard time for the entire world, to prevent misunderstanding and to provide a standard time for comparison. It creates a time lag of two hours from Gujarat to Arunachal Pradesh. The local times that lie on various meridians are bound to vary. Compared to Gujarat, the sun rises two hours earlier in Arunachal Pradesh.

Your local time can be defined by the longitude and latitude of your area. But in one region, it is difficult to apply distinct local times because of local time changes in every area.

Let’s take an example. Suppose you live in Gujarat and go on a tour of West Bengal and buy a wristwatch. But it displays the local time of that venue. You have purchased it and you are leaving West Bengal. You come back on the train. The train started and Patna arrived. You need to fix your local time for Patna. Bhopal came then. You've got to schedule your local time for Bhopal. Then Ahmedabad has finally arrived and you have to set the time on your wrist watch again.

This is where Standard Meridian or 82°30' Eastern Longitude makes it easier. As it passes through the centre of the nation, the local time at this Meridian has been recognised as the Indian Standard Time (IST) throughout the nation. It has helped to prevent a lot of misunderstanding by adopting various local times or in the absence of a standard period that would have been there.

The watches show that the planet takes 4 minutes to rotate around 1° of longitude at the same time, so it takes 1(15° x 4 mins=60 mins) hour for the earth to rotate through 15 degrees of longitude.

Since India has a 30-degree longitudinal range, there is a 2-hour time difference between Arunachal Pradesh and Gujarat, but the watches are set at 82.5° for all parts of the country according to the Indian Standard Time, which is why the watches display the same time everywhere in India. All watches in the country run according to the standard time. There is a time lag of 2 hours from Arunachal Pradesh to Gujarat, but the watches show the right time.

Note:
In India, Allahabad's local time is known as India's standard time. So, whether you're in West Bengal, or you're in Gujarat, or you're in Kashmir, or you're in Kanyakumari, your watch would be at the same time.