how to calculate time using longitude

Solution(By Examveda Team)

Because one day is 24 hours long one can easily use time to calculate longitude. One hour of time difference corresponds to 15° of longitude (360°/24 hours = 15°/hour). Suppose an observer sets his accurate watch to 12:00 at noon in Greenwich, England and then travels a great distance. The observer then notices that the sun is highest in the sky at 4:00 according his watch. The observer then knows he is at longitude 60° W (4 hours ×15°/hour = 60°).

It should be pointed out that “noon” in general does not mean 12:00 PM. Rather, it is the time when the sun is highest in the sky. Because of the use of timezones the sun will be highest in the sky from about 11:30 AM to 12:30 PM local time for an observer. If longitude is known, the time of astronomical noon can be calculated.

For example, Lincoln, NE, is at longitude 96.7° W. 96.7°/(15°/hour)=6.4467 hours. Being Central Time, Lincoln is 6 hours away from Greenwich Mean Time, so astronomical noon is (6.4467 - 6) hours = 0.4467 hours = 26.8 minutes from 12:00. Thus “noon” in Lincoln, Nebraska is about 12:27 PM (1:27 PM during daylight savings).