The time zones of the world were created in 1884 by some of the world's renowned scientists. They were created so that we have a uniform way of telling time in all parts of the world. The clock could not be set on the same time because earth is round and if there is day time in part, the other will be having night time. This is why Greenwich Mean was created. Greenwich Mean Time is the standard time for the whole world. The time zones have been created on the basis of dividing the world into vertical slices (virtually) starting from England. The world is divided by virtue of 24 slices which are at the width of 15 degree longitude each and have one hour of time difference. The concept of time zones is based on degrees of longitude. The time zones change as you move from the North Pole to the South Pole and so does the time difference.