Greenwich Mean Time (GMT) may be the time measured around the Earth’s zero degree line of longitude, or meridian. This runs in the North Pole towards the south Pole, passing with the Old Royal Observatory within the London suburb of Greenwich.
Keeping this in consideration, where’s the meridian line?
A (geographic) meridian (or line of longitude) may be the 1 / 2 of an imaginary great circle around the Earth’s surface, ended through the North Pole and also the South Pole, connecting points of equal longitude, as measured in angular levels east or west from the Prime Meridian.