Question

why do we use Standard Time?

Answer 1

Because the time varies from place to place in India itself, as the sun rises two hours earlier in Arunachal Pradesh, than Gujarat. Therefore, the time along the standard meridian passing through Mirzapur, Uttar Pradesh, in India, has been taken as the standard time for the whole country..

..hope this answer helps :)

Answer 2

Standard time is the synchronization of clocks within a geographical area or region to a single time standard, rather than using solar time or a locally chosen meridian (longitude) to establish a local mean time standard.