passes (longitude 0° 0' 0"), which forms the reference for Greenwich Mean Time. From the zero meridian of longitude at Greenwich, the globe is divided into west and east longitudes, each 180°.
GMT time is the time that prevails at Greenwich Observatory, England. It is the time reference for astronomical time and is also referred to as UT1, which stands for Universal Time 1. The GMT time scale UT1 and Coordinated Universal Time (UTC) differ slightly, which is compensated for by the leap seconds inserted. Greenwich Mean Time has been replaced by Universal Time Coordinated (UTC), which is the coordinated world time.