Hint: The Earth has been distributed into twenty-four time zones of an hour each. All of these zones meet fifteen degrees of longitude. Since the local time varies by four minutes at each longitude, it would generate a lot of confusion concerning time for any country entirely, which may extend across several longitudes.
Accordingly, each country chooses a central meridian. The local time of this Meridian will be the standard time of the country. The standard times which prevail on various meridians are made to differ. The sun rises almost two hours earlier in Arunachal Pradesh when related to Gujarat. This causes a time delay of two hours from Gujarat to Arunachal Pradesh to evade confusion and to possess a standard time for reference. The \[82.30\]' Eastern Longitude will be taken as the standard time for the entire country. The time at this Meridian has been affirmed as the Indian Standard Time (IST) entirely around the country as it passes within the center of the country. It has served to avoid confusion that would have arisen by following separate local times or in lack of a uniform time. \[82\]degree $30$ minutes is chosen as standard Meridian mainly because it lies almost in the middle of India. It has stopped a lot of uncertainty from one place to another and has brought peace in time everywhere in the country. The local time of longitude is modified, so, to follow one timing, we have believed \[82\] degrees \[30\] minutes to be the standard Meridian.
Note: The standard Meridian of India at \[82'3\] e at Mirzapur in Uttar Pradesh was taken as the standard Meridian because it splits the country into closely two equal parts The \[82.50\]E longitude is smaller than $1$ km from the famous Vindhyavasini temple. Ghamapur is now known as India's Greenwich.