Question

Why it is 5:30pm in India when it is 12pm in London?

Answer 1

Its coz of rotation and revolution of the earth and India follows IST (Indian standard time) hence time varies from one country to other.Hence it varies. IST of  Indian standard time is with difference of 5:30 hours with the greenwich meridian time which passes through London. Hence there is difference of time between london and india..

Answer 2

there are four main reasons behind this-
#earth's revolution
#earth's rotation
#distance
#greenwich meridian