Each Time Zone represents 1 hour and is represented by the corresponding color coded areas at the bottom of the Map. Eastern Standard Time is 5 hours from Greenwich. Central Standard Time is 6 hours from Greenwich and so on.

       Throughout early American history, cities and towns developed a tendency towards making Time a local matter,- referring either to a church steeple or some locally known clock as a standard.

      As early as 1809, William Lambert, an amateur Astronomer, recommended that Congress adopt a system of Time Meridians. In addition to this, the continuing westward expansion of the United States, mostly helped by the railroads, brought further attention to the fact that different states and localities were all keeping their own time.

      As a result, it would be entirely possible for someone to leave South Carolina at 2 pm and travel westward for a couple of hours, then arrive in a midwestern or western town or city only to find that the time there was 12 pm.

      In 1870, at the suggestion of Charles Dowd, a teacher from Saratoga Springs, N.Y., a full system of time zones, each 15 degrees wide, and each containing one hour of time, was published by the committe of railway superintendents of New York, in a pamphlet entitled "A System of National Time for Railroads". Each time zone was simply called the first, second, third and fourth zones.

      After minor revisions in 1872, it took another eleven years before this concept of Standard time, was adopted by the railroads on November 18, 1883. This would come to make time no longer a local matter and travelers going East or West would have a more reliable system of time they could depend on.

      Yet, small towns and cities were slow to adapt to this, and it wasn't until March 19, 1918, a full 35 years later, and after the inception and widespread use of the automobile, that the Government instituted The Standard Time Act, which officially recognized into law, the different time zones that differentiate sections of the United States

      Thus, Daylight Saving Time was established. Yet, a year later, when World War I ended, in 1919, it was repealed. The concept of Time Zones was kept in law with the Interstate Commerce Commission assigned to determine the boundaries of each time zone.

      During World War II, in an effort to give war factory workers an extra hour of daylight to help increase their production, Daylight Saving Time was re-constituted as "War Time", and kept year round from 1942 to 1945 when the war ended.

      When the War ended, the use of Daylight Savings Time became rather spotty from one locality to another, until it was standardized by the Uniform Time Act of 1966, which specifically denoted dates for the beginning and end of its observance with some local exeptions.

      Eventually, the authority over time zone boundaries, held previously by the Interstate Commerce Commission, was changed over to the U.S. Department of Transportation. Then all of the Time Zones except the Eastern Time Zone were renamed.

      Time Zone boundaries are still changing, with most of these occurring in areas that are near Time Zone boundaries. While there has been some trend for boundaries to shift westward, more often than not, most changes are made because of the law's accomodation of suggestions that favor the "convenience of commerce." For the time being, this seems to be a reasonable guideline for determination going forward.