82° 30' E
Explanation
Local time varies with longitude. To ensure a uniform time system across the country, a specific central longitude is designated as the Standard Meridian. The time along this meridian is adopted as the official time for the entire nation, known as Indian Standard Time (IST).
Detailed Analysis:
- Longitudinal Extent: India's longitudinal extent ranges roughly from 68° 7' E in the west to 97° 25' E in the east. This difference of approximately 30 degrees results in a time lag of about two hours between Gujarat and Arunachal Pradesh.
- Selection of Standard Meridian: To neutralize this time difference, the longitude of 82° 30' E (82 degrees 30 minutes East) is accepted as the Standard Meridian of India. It passes through the approximate center of the country's longitudinal spread.
- Geographical Reference: This meridian passes through Mirzapur (near Prayagraj) in Uttar Pradesh.
- Global Relation: Indian Standard Time is 5 hours and 30 minutes ahead of Greenwich Mean Time (GMT).
Key Takeaway:
The 82° 30' E longitude determines the Indian Standard Time (IST) to maintain a single time zone for the entire country.