by Michael Totten

Created on: December 20, 2011   Last Updated: December 22, 2011

Although both the United States and Europe occupy multiple time zones, they do not overlap at any point. Not counting differences in daylight savings time and overseas territories, the closest they get is 5 hours apart, which is the difference between Greenwich Mean Time (GMT/UTC), the time zone of Great Britain and Western Europe, and Eastern Standard Time (EST/UTC-5), the time zone of the Atlantic Seaboard.

There is a time difference because the Earth's rotation causes the sun to rise in Europe before it rises in the United States. The exact time difference is because of time zones.

Before time zones became the standard, each city set its own time by the sun. When worldwide standard time was proposed by Sandford Fleming in 1879, it divided the world into 24 time zones. Thereafter, every place in a time zone would set its clocks to exactly the same time or sometimes to a fixed fraction of a standard zone, even if their solar times were different. After the system was adopted globally  in an amended form, each city sets its time based on time zone difference from GMT, which was later adjusted to Universal Coordinated Time (UTC).

For navigation purposes, the Earth is divided into 360 degrees of longitude, the same number of degrees as a full circle. Because standard time is based on a 24-hour universal day, time zones divide total longitude into 24 equal parts. Each time zone occupies approximately 15 degrees of longitude.

On average, Europe and the United States are roughly a third of the world apart. As a result, the time zones Europe and the United States occupy are also roughly a third of the universal day apart, which averages around 8 hours between continental America and continental Europe. Both Europe and the United States occupy multiple time zones, so the difference can be as little as 5 hours or as much as 14.

The continental United States occupies 4 time zones: Eastern, Central (CST/UTC-6), Mountain (MST/UTC-7), and Pacific (PST/UTC-8). Alaska and Hawaii add 2 more time zones: Alaska (AKST/UTC-9), and Hawaii-Aleutian (HAST/UTC-10).

Without counting Russia, Europe occupies 3 time zones: Eastern European (EET/UTC+2), Central European (CET/UTC+1), and Greenwich Mean Time, which also doubles as Western European Time (WET/UTC). Until 2011, the former Soviet republics in Europe added 2 more time zones: Moscow (MSK/UTC+3) and Samara Time (SAMT/UTC+4).

In March 2011, Russian time zones changed when Russia adopted daylight savings time year-round. Belarus followed in September 2011. As a result, Samara Time is no longer used. Moscow is now permanently at UTC+4 and Kalingrad and Minsk are now permanently at Further Eastern Time (FET/UTC+3).

A few places do not use the time zone they belong to geographically. Instead, they use the time zone of the major nearby place with which they do the most business. For example, most of Indiana uses the time zone of nearby Chicago (CST), rather than its geographical one (EST). Similarly, a tiny bit of Maine uses EST to fit in with the rest of the Atlantic Seaboard, although geographically it would be part of Atlantic Standard Time (AST).

Iceland is a more extreme exception. It uses GMT to make business with Great Britain and the rest of Europe easier. If Iceland used its geographical time zone instead, the western coast of Iceland would only be 3 hours ahead of the Atlantic Seaboard instead of 5, but it would be out of step with Great Britain by as much as 2 hours.

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