With globalization, there came an increasing need for the standardization of time zones, particularly for transportation (namely railways) and communications across longitudes. While mariners began developing a system for tracking time zones, the concept flourished in the 1800s, when railroads became a popular mode of transportation.
Various methods for standardized time zone system were proposed throughout the mid-nineteenth century, which divided the United States into several time zones, each an hour apart. The worldwide system was proposed by Sandford Fleming in 1879, which divided the earth into 24 time zones, beginning at Greenwich, the 180th meridian, and each 15° apart.
Today, these world time zones are followed as shown on the map above. Most countries follow the hourly deviations, though they do not always align with longitudes for convenience, in order to incorporate the entire country. Some countries, including India and Iran, use half-hour deviations instead, and some choose to use just one time zone for the entire country, like China.
Last Updated On : October 10, 2012