Question

time is mesured from which longtitude

Answer 1

Finding Longitude. 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.

Answer 2

from the Greenwich meridian which is an imaginary longitude passes through London is calculated as standard tume