"What then is time? If no one asks me, I know what it is. If I wish to explain it, ...I do not know."
Saint Augustine, theologian
A time zone is a longitude band around the globe in which everyone sets their clocks to the same time— regulated by the movement of the sun. Before time zones were introduced, every town kept its own local time. But with the advent of the railways this system became very inconvenient, as the time at the starting point of a journey might well differ from the one at the terminus. In 1847 the railway companies in Great Britain recommended that all docks should be set using the same time marker. Noon on the Greenwich Meridian (0 degrees longitude) was chosen, which is known as Greenwich Mean Time (G.M.T.).
Because Earth spins every twenty-four hours, local time varies by one hour for every 15-degree change in longitude. Scottish-born engineer and inventor Sir Sand ford Fleming (1827-1915) recognized this and suggested that not only should continental America have four meridians, but that similar 15-degree time zones should be established all over the globe.
In 1884 the Fleming plan was accepted for the whole world at the International Meridian Conference in Washington, D.C, and the Greenwich Meridian was chosen as the prime meridian.
