What is Greewich Mean Time (GMT)
Greenwich Mean Time (GMT) is clock time at the Royal Observatory in Greenwich, London. Greenwich Mean Time (GMT) was established at the International Meridian Conference in 1884. Greenwich Mean Time (GMT) is based on time at prime meridian. Prime meridian is the longitude in a geographic coordinate system where the longitude is 0°. Longitude is the angular distance east or west on the earth's surface.
Below image shows the map where prime meridian is marked.
Image credit - commons.wikimedia.org
Following image shows the Shepherd gate clock at the Royal Observatory in Greenwich, England.
"Shepherd Gate Clock" by Tommi Komulainen is licensed under CC BY-NC-SA 2.0
