Gujarat in the west but the watches show the same time. How does this happen

Answer: The longitudinal gap between Arunachal Pradesh and Gujarat is about 30°. Due to this, there is time lag of about two hours between these states. Since Arunachal Pradesh is in the east hence the sun rises earlier here; compared to in Gujarat. 

The Indian Standard Time is taken from the time of Standard Meridian of India and hence the watches show the same time in both the states.