Geography question from JKAS Prelims, 2022 by JKPSC
If the time at Greenwich Meridian is 12:00 AM (Midnight), what would be the time at 30°W meridian?
Last updated Jun 24, 2026
Correct Answer:
Option B —
10:00 PM
This calculation is based on how the Earth rotates in relation to time and longitude.
The Logic of the Calculation
1. The Relationship Between Distance and Time
The Earth takes twenty four hours to complete a full rotation. Because a full circle consists of three hundred and sixty degrees, we can determine that the Earth rotates fifteen degrees every hour. This means that for every one degree you move, the time changes by four minutes.
2. Calculating the Two Hour Difference
Since the location in the question is thirty degrees away from the starting point at Greenwich, we multiply those thirty degrees by the four minutes per degree. This gives us a total of one hundred and twenty minutes, which is exactly two hours.
3. Determining the Direction
A simple rule to remember is that time is ahead as you move East and behind as you move West. Because the question specifies thirty degrees West, the time at that location must be earlier than the time at Greenwich.
4. The Final Result
If it is exactly Midnight at the Greenwich Meridian, we must count back two hours to find the time at the Western location. Moving back one hour brings us to eleven at night, and moving back a second hour brings us to ten at night.
Summary for Time Zones
Moving East: Add four minutes for every degree.
Moving West: Subtract four minutes for every degree.
Fifteen Degree Blocks: Each fifteen degree section represents a one hour difference.
Answer verified by Quintessence Classes faculty — Karan Nagar, Srinagar.
