Canadian Sandford Fleming invented Standard Time in 1879. He proposed that the world should be divided into 24 equal Time Zones, and that the time within each zone would be the same. Up until then, it had varied from community to community. The railways were the first to adopt the idea and by 1890 all countries had adopted the Standard Time system. Prior to that the U.S. had about 300 local times. Sanford Fleming was knighted in 1897 for his idea.
Each Time Zone contains 15 degrees of longitude. The first time zone is located at Greenwich in England.
There are irregularities caused by the demands of geography and the desire to keep a constant time within some political boundaries. For example, Newfoundland is split down the middle by a time zone boundary. In typical Newfie fashion they decided to split the difference - thus it's always half an hour later in Newfoundland as compared to atlantic standard time.