Why does this happen?
This happens because India follows a single Indian Standard Time (IST) across the entire country. Although there is a variation of nearly 30 degrees in longitude between the easternmost and westernmost parts of India, which causes a time difference of nearly two hours, all watches show the same time.
The sun rises in the northeastern states about two hours earlier as compared to Jaisalmer, but the watches in Dibrugarh, Imphal in the east and Jaisalmer, Bhopal or Chennai in other parts of India show the same time. This uniformity is maintained by adopting a standard meridian (82°30'E) for the whole country, which serves as a common reference for timekeeping.
Explanation
The textbook explains that India's longitudinal extent of nearly 30 degrees naturally creates a time difference of about two hours between its eastern and western extremes. However, to maintain administrative convenience and uniformity, India adopts a single Standard Meridian (82°30'E) for the entire country. This is why despite the sun rising earlier in the northeast, all watches across India display the same time based on IST.