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Time Zones

We all know about world timezones, but how many of us have really thought about them?

Timezones are an artificial, man-made response to a natural phenomena: as the Earth revolves, the sun reaches noon at different times across the globe. When it is midday somewhere, it is midnight somewhere else.

That rather obvious fact causes problems when trying to coordinate time across the world. When I say "10 AM" in London, what will that mean to someone in New York? We could just pick the time at some place and define that as the standard. In fact that is exactly what we have done. Today we use Coordinated Universal Time (UTC) which is in effect the same as Greenwich Mean Time (GMT) for everyday use. GMT itself is purely an artificial creation - the "prime meridian" could be placed anywhere, and indeed often was before the universal adoption of GMT.

Obviously it would be unhelpful for the entire world to use UTC, since this would result in some countries having noon at night! Hence we need a system of translating UTC into its equivalent elsewhere. That is what world Time Zones are, a translation mechanism.

Longitude

Timezones are intimately connected with longitude. Different degrees of longitude will see noon at different times, this difference being measured in minutes.

In reality, every single degree of longitude has its own time zone, however this would be impossibly complex to use. So a trade-off between useability and accuracy was made. We thus have 24 different world Time Zones and local time is coordinated across each zone. In reality, solar noon occcurs at slightly different times across any one zone, however the difference is rarely a matter of concern.

The 24 nautical time zones are each designated by a letter of the alphabet. GMT is represented by "Z" so GMT/UTC is sometimes known as "Zulu Time".

Timezones are theoretically 15 degreees of longitude wide. In reality they follow the boundaries of states and countries and tend to be irregular over land. In some countries, several Timezones are merged to form one larger local time measurement.

A result of all this is that a Time Zone map is, quite honestly, a mess - but it works!

	All About Clocks, Watches and Time
Time Zones We all know about world timezones, but how many of us have really thought about them? Timezones are an artificial, man-made response to a natural phenomena: as the Earth revolves, the sun reaches noon at different times across the globe. When it is midday somewhere, it is midnight somewhere else. That rather obvious fact causes problems when trying to coordinate time across the world. When I say "10 AM" in London, what will that mean to someone in New York? We could just pick the time at some place and define that as the standard. In fact that is exactly what we have done. Today we use Coordinated Universal Time (UTC) which is in effect the same as Greenwich Mean Time (GMT) for everyday use. GMT itself is purely an artificial creation - the "prime meridian" could be placed anywhere, and indeed often was before the universal adoption of GMT. Obviously it would be unhelpful for the entire world to use UTC, since this would result in some countries having noon at night! Hence we need a system of translating UTC into its equivalent elsewhere. That is what world Time Zones are, a translation mechanism. Longitude Timezones are intimately connected with longitude. Different degrees of longitude will see noon at different times, this difference being measured in minutes. In reality, every single degree of longitude has its own time zone, however this would be impossibly complex to use. So a trade-off between useability and accuracy was made. We thus have 24 different world Time Zones and local time is coordinated across each zone. In reality, solar noon occcurs at slightly different times across any one zone, however the difference is rarely a matter of concern. The 24 nautical time zones are each designated by a letter of the alphabet. GMT is represented by "Z" so GMT/UTC is sometimes known as "Zulu Time". Timezones are theoretically 15 degreees of longitude wide. In reality they follow the boundaries of states and countries and tend to be irregular over land. In some countries, several Timezones are merged to form one larger local time measurement. A result of all this is that a Time Zone map is, quite honestly, a mess - but it works! Clocks-Watches-Time / Time / Zones / All original material copyright © Trevor Mendham 2005-2008. All trademarks are the property of their respective owners Please read the site terms of use		Clocks Watches Time 60 24 Hours 7 Days Arrow Atomic Bells Biological Calendars Daylight Saving Leap Seconds Planck Quotes Solar Standard Travel Zones Time & Motion More...