How does the Greenwich clock work?

The Eastern time zone in the United States is designated as GMT minus five hours. When it is noon in the Eastern time zone, it is 5 p.m. at the Greenwich Observatory. ... A bunch of astronomers declared the Greenwich Observatory to be the prime meridian at an 1884 conference. read more

Time at the Greenwich Meridian is known as Greenwich Mean Time (GMT) or Universal Time. The Eastern time zone in the United States is designated as GMT minus five hours. When it is noon in the Eastern time zone, it is 5 p.m. at the Greenwich Observatory. read more

Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London. GMT was formerly used as the international civil time standard, now superseded in that function by Coordinated Universal Time (UTC). read more

Working Principle of Atomic Clocks. In an atomic clock, the natural oscillations of atoms act like the pendulum in a grandfather clock. However, atomic clocks are far more precise than conventional clocks because atomic oscillations have a much higher frequency and are much more stable. read more