What geographical features distinguish it?

Answer 1

15 degrees because for every 15 degrees of longitude that you move, you enter a new time zone. As you move west, you gain an hour; as you move east, you lose an hour. There are 360 degrees on the Earth, which divided by 24 hours in the day, give 15 degrees of longitude per time zone. You can calculate the time by knowing the longitude of two locations and a time at one of them. By measuring the difference in longitude and dividing it by 15, you arrive at the time of the second location.