This clock shows the local time as it is stored in your computer. Oh, yes, by the way, this is a picture of my father's watch.
In the past, when the slowness of transports made short travels last several days, nobody, except the astronomers, could understand that the solar time at the same moment is different from place to place.
Indeed, if in a certain place the Sun is at noon position, in a more western place at the same instant of time the Sun has not yet reached the noon position, while the contrary happens for a more eastern place.
If two places are exactly aligned along the north-south direction, they have the same solar time, because they see the Sun forming the same hour angle with the noon position.
This alignment, defined geographically as meridian, is given by the half-circle passing for these places and terminating at the terrestrial poles.
In several places in the world, hundreds of different times were adopted, each one corresponding to its own meridian.
GMT: Greenwich Meridian Time UTC: Unified Co-ordinated Time
Around the half of 1800, with the coming of faster transport and world-wide communication systems and the growing need to have an accurate time reference for sea navigation, the Greenwich Mean Time (GMT) (later called Universal Time or UT) was introduced.
UT time is measured with astronomical techniques at the Greenwich astronomical observatory in England.
The UT time corresponds with good approximation to the mean solar time of the same observatory.
Until the first half of 1900, the highest accuracy of time measurements was carried out by means of astronomical observations.
This situation changed in 1955 when the first caesium atomic clock was built, after twenty years of research in several scientific laboratories.
To make it simple, we can say that the atomic clock is an electronic device that measures time counting atom oscillations.
Since communication signals can cross multiple time zones and the International Date Line, some worldwide standard for time and date were needed.
This standard is co-ordinated universal time, abbreviated UTC, formerly known as Greenwich Mean Time (GMT).
Other terms used to refer to it include "Zulu time" (after the "Z" often used after UTC times), "universal time", and "world time".
BMT: Biel Meridian Time
BMT
BMT
@000
Internet Time is a "new" way to tell time invented and marketed by the Swiss watch company Swatch.
The current Internet Time is the same all over the World (no time zones or daylight saving time adjustments).
Instead of dividing the virtual and real day into 24 hours and 60 minutes per hour, the Internet Time system divides the day into 1000 ".beats".
Each .beat is 1 minute and 26.4 seconds.
Internet Time is based on a new Meridian (as opposed to the Greenwich Meridian).
This new Meridian goes through Swatch's office in Biel, Switzerland and is called the BMT Meridian.
BMT or Biel Mean Time is linked up to the Central European Winter/Standard time - which is UTC + 1 hour.
When it is Midnight in BMT, the Internet Time is @000 beats, Noon is @500 beats.
NET: New Earth Time
New Earth Time is a smooth system that goes round the clock in 360 intervals of 4 minutes.
As opposed to the 1 minute and 26,4 seconds of a ".beat", NET looks more like a "natural" system, unifying time, but not disturbing our habits.
Its principals are very simple :
There is one NET world-wide. 240 degrees occurs at the same moment in Sydney, New York, Brussels and Beijing.
The NET day begins on longitude zero at Greenwich.
A day divides to 360 degrees. One degree is composed of 60 net-minutes. And a net-minute is divided into 60 net-seconds.
Each net-degree is exactly 4 minutes long. There are exactly 15 degrees every hour. A net-second corresponds to 1/15 of a conventional second.
UTC-midnight is equal to 0° and UTC-noon equals 180°.
The big hand of this clock shows the NET time
and local time, on a 24 h basis, is found on the outer dial (based upon the timezone setting of your computer).
The small dial at the left indicates NET minutes
and the one at the right indicates your local time.
The upper text display gives the NET time in digital format
and the lower text display indicates the date in a dd.mm.yyyy format.
More information
A Walk through Time is a very nice overview of the history of time measurement.
Computer clocks are not always very accurate.
Neutron is a small and free program to synchronise your computer with an atomic clock.
Many sites offer information about UTC
A visit to the site of the BIPM (Bureau International des Poids et des Mesures) is very instructive (don't worry, their site is in english).
The fourmilab (ant laboratory), maintained by Autodesk's founder, John Walker, offers superb views of day and night zones on earth.
A lot of references can be found on the web about BMT
Around the half of 1800, with the coming of faster transport and world-wide communication systems and the growing need to have an accurate time reference for sea navigation, the Greenwich Mean Time (GMT) (later called Universal Time or UT) was introduced.
UT time is measured with astronomical techniques at the Greenwich astronomical observatory in England.
The UT time corresponds with good approximation to the mean solar time of the same observatory.
Internet Time is a "new" way to tell time invented and marketed by the Swiss watch company Swatch.
The current Internet Time is the same all over the World (no time zones or daylight saving time adjustments).