Greenwich Mean Time (GMT)
The name of the twenty-four hour time scale which is used throughout the scientific and military communities. Standard Time begins at Greenwich, England, home of the Royal Observatory which first utilized this method of world time. This is also the Prime Meridian of Longitude. The globe is divided into twenty-four (24) time zones of 15 degrees of arc, or one hour in time apart. To the east of this meridian, time zones are number from 1 to 12 and prefixed with a minus (-), indicting the number of hours to be subtracted to obtain Greenwich Time (GMT). To the west, the time zones are also numbered 1 through 12, but are prefixed with a plus (+), indicating the number of hours to be added to obtain GMT.
Related terms: Universal Time Coordinate (UTC) and Zulu (Z)
Longitude
The location east or west in reference to the Prime Meridian, which is designated as zero (0) degrees longitude. The distance between lines of longitude are greater at the equator and smaller at the higher latitudes, intersecting at the earth’s North and South Poles. Time zones are correlated to longitude.
Universal Time Coordinate
One of several names for the twenty-four hour time which is used throughout the scientific and military communities.
Zulu Time
One of several names for the twenty-four hour time which is used throughout the scientific and military communities.