The sun rises two hours earlier in Arunachal Pradesh as compared to Gujarat in the west but the watches show the same time. How does this happen?

Time is measured by the longitudinal line at any place in the world.

We see the same time at any place in India because India follows time which is measured according to the longitude of Standard meridian i.e. Indian Standard Time.

i. Longitude of Standard Meridian is 82.5 degrees with respect to Greenwich Line which is 0-degree longitude.

ii. India follows one-time zone so that people of India does not have any confusion when they are travelling from north-west to north-east region.

iii. Illiterate people of India can find it very difficult to change the time reflected by their watch according to different time zones.

NOTE: 1 longitude degree is equal to 4 minutes. Difference between longitudes of Arunachal Pradesh and Gujarat is 30 degrees. Therefore, the difference between their time is 4× 30 =120 minutes = 2hours.