greenwich civil time การใช้

• HM Nautical Almanac Office in the United Kingdom used Greenwich Mean Time ( GMT ) for both conventions, leading to ambiguity, whereas the Nautical Almanac Office at the United States Naval Observatory used GMT for the pre-1925 convention and Greenwich Civil Time ( GCT ) for the post-1924 convention until 1952.
• A later version of Washington mean time based on the merdian of the clock room at the exact center of the New Naval Observatory ( 77?2 2.243 W or 816.15 } } ) was still being used in 1950 on a few pages of the " American Ephemeris and Nautical Almanac ", even though most of its pages used Greenwich Civil Time, the American name for the midnight epoch Greenwich Mean Time.