If the earth’s direction of rotation is reversed, what would be the IST when it is noon at the International Date Line?

1. 06.30 hrs
2. 05.30 hrs
3. 18.30 hrs
4. 17.30 hrs

Explanation

Option (c) is correct

• Normally, the Earth rotates from west to east, so places in the east are ahead in time. IST (82.5° E) is therefore 6 hours 30 minutes behind the International Date Line (180°). If the Earth’s direction of rotation were reversed, time calculation would also reverse, and places to the west would become ahead in time. Since IST lies west of the International Date Line by 97.5° longitude, IST would be 6 hours 30 minutes ahead of it. Therefore, when it is 12:00 noon at the International Date Line, IST would be 18:30 hrs (6:30 PM).

Answer: (c) 18:30 hrs