Question

How can we measure the time difference between countries explain giving an example

Answer 1

We can measure from Greenwich Meridian.
If it is 12 noon in India,we know that difference between two longitudes is 2 min ,Greenwich Meridian is 0 and IST is 87.5 longitude so the time difference will be 5hr 30 min or 330 min.
Here we are multiplying 87.5×4.

Answer 2

we can measure the time difference between countries by measuring the standard greenwich time for example India is 5 and half hour before London.