Why is the east coast three hours ahead of the west coast?

Answer 1

It's because time is based on the position of the sun, and the sun rises in the east and sets in the west. It takes three hours longer for sunrise to hit the west coast than the east coast.

Answer 2

The time difference between the east coast and the west coast of the United States is due to their respective positions within different time zones. The Earth is divided into 24 time zones, each roughly 15 degrees of longitude wide. When it is noon on the east coast, it is 9 am on the west coast due to the Earth's rotation.