the time measured on the Earth's zero degree line of longitude, or meridian. This runs from the North Pole to the South Pole, passing through the Old Royal Observatory in the London suburb of Greenwich.
Greenwich Time is the same as Universal Time, or UTC. Unlike the time zone times, UTC can be used anywhere in the world, without changing the time. Also, they use the 24 Hour Clock format. So there is no AM or PM status for UTC.
