Did you know that Atomic Time, "is the most accurate realization of a unit that mankind has yet achieved?" Learn about this and other systems of time and how they are used.

A map from 1910 of the United States showing the time zones as they were then established. Clock-symbols at the bottom of the map show the comparative times when it is noon in London. "Formerly every city used its own sun time, or local...

A map from 1872 of the West Indies and Central America. The map shows political boundaries at the time, capitals, major cities, and ports, railroads, main steamship routes, rivers, terrain and coastal features, and banks. The map shows...

A map of Asia from 1872, showing physical features including mountain systems, deserts, lakes, rivers with direction of flow, coastal features, and ocean currents, political boundaries and foreign possessions at the time, and commercial...

A map from 1872 of Rhode Island, with map inserts of Providence, Newport, and Block Island. The map shows counties and county seats, principal cities, ports, and towns, railroads, terrain and coastal features, and rivers. Clock symbols...

A map from 1910 of the United States showing the railway network and connecting steamship lines. This map distinguishes the transcontinental railroads and secondary lines, and shows the standardized time zones used in 1910. The clock...

A commercial map from 1872 of the United States showing the principal railroad and steamship routes in the region at the time. The map shows state boundaries and capitals, major cities and ports, submarine telegraph cables to Europe,...

A map from 1872 of Maine showing the State capital of Augusta, counties and county seats, major cities, towns and ports, railroads, mountains, lakes, rivers, and coastal features. An inset map details the vicinity of Portland. Clock...