What is the definition of Greenwich mean time, and is it the same as zulu time ?
If you’re not bothered about accuracy of less than a second, then you can take Zulu as being the same as Greenwich Mean Time. Greenwich Mean Time is the hour angle of the Mean Sun at the meridian of Greenwich. Greenwich Mean Time was renamed Universal Time (UT) but because of the variability in the Earth’s rotation, UT (GMT) is not a uniform time system and was replaced in 1972 by Coordinated Universal Time (UTC) which is fixed at an exact number of seconds different from International Atomic Time, thus is a uniform time system, but with leap seconds introduced at suitable intervals in order not to depart from UT by more than 0.9 seconds. UTC is used as the basis for the world’s time systems and is referred to as Zulu for aviation purposes.
