Time in countries to the east of the Prime Meridian is always in front of that in the UK. Time in countries to the west of the Prime Meridian is always behind that of the UK. Image caption ...

The prime meridian is at 0 degrees longitude, extending east and west. Under this system, an exact location on the earth's surface can be expressed as a set of numbers. The latitude and longitude ...

A line marks the 'Prime Meridian of the World' at Longitude 0 degrees at the Royal Observatory in Greenwich on March 26, 2012, in London. Oli Scarff/Getty Images The 1884 International Meridian ...

Measuring longitude (east or west) was harder. Airy developed an accepted prime meridian line from the observatory at Greenwich, which became zero degrees longitude. It became a global benchmark ...