asianflava wrote:GMT is Greenwich Mean time, Zero time, or Zulu time. It is the designated place where one day ends and the next begins. 0deg 0min 0sec Longitude.
Here is today's history lesson.
Greenwich Mean Time was 'created' when the advent of railways in Britain highlighted that different cities were using different times and matching the train timetables to a variable local time was proving impossible. So a standardised time for Britain was created and the Royal Observatory at Greenwich defined it. The full story is
here.
You might find the
GMT web site useful - I find it a reasonably accurate way of setting my PC clock.
A separate issue is the Prime (or Greenwich) Meridian which defines where east and west start. This was the subject of much discussion that was eventually settled between the European countries when Britian indicated that it would consider recognising the metric system if everyone agreed to use Greenwich as the prime meridian*. As Britain was the dominant world power at the time, a lot of the world was using British nautical charts which put 0 deg at Greenwich, so it was the easiest way to go.
And here's a Dave from Penn State Uni doing the right thing on a visit to Greenwich by standing astride the Prime Meridian, with one foot in the western hemisphere and the other in the east:
(Brnnnnnng!) That's the end of class for today.
Andrew
* I believe the alternative was that the British delegation to the conference were going to gather up all their toys and not let the other children play with them, so everyone quickly agreed.