The latitudinal and longitudinal extent of India is about 30°. The time along the Standard Meridian is taken as the Indian Standard Time. The Standard Meridian of India passes through Mirzapur in UP which is located at 82°30’ east. The time lag between Arunachal Pradesh (in the east) and Gujarat (in the west) is about 2 hours. When one moves from south to north, the latitudinal extent influences the duration of day and night.

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83 degree 30' e has been selected as the standard meridian of India as it is the only latitude which passed through nearly half of the country India.
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