to calculate the difference between the local times of any two places on the earth, 1.the noon time at both the places should be known 2. the difference in degrees of their longitudes be known 3.the difference in standard times of both the places should be known 4. change need to be made according to International Date line .

to calculate the difference between the local times of any two places

1.	to calculate the difference between the local times of any two places on the earth, 1.the noon time at both the places should be known 2. the difference in degrees of their longitudes be known 3.the difference in standard times of both the places should be known 4. change need to be made according to International Date line .
Answer» The answer is 3. To compare local times, we NEED to compare the standard times of the particular local TIME... For example GMT is 00:00 and IST: is +05:30. So to CALCULATE DIFFERENCE between Mumbai and London times, we just calculate the difference in the standard times.