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    Re: What happened to the leap second?
    From: David C
    Date: 2017 Jan 2, 15:34 -0800

    I am struggling to get my head around this. From the quotes above I deduce:

    UT1 variable length second

    UTC fixed length second

    UTC second slightly less than UT1 second

    I think that I have finally simplified the subject to five lines. I have appended them below.

    I think it is time that I gave this subject a rest.  I will be back when I hear from either Radio NZ or MSL (Measurement Standards Laboratory of NZ) about the missing time pip.

    TAI is atomic time.

    UTC is offset from TAI. It is the time used by humans. "Coordinated" means that there is a network of clocks.

    The "UT" in the Air Almanac is UTC.

    UT1 is earth time. Celestial navigators time observations by UTC but celestial bodies "observe" UT1. Therefore UTC - UT1 must be kept small  (by convention < 0.9 sec). The leap second is the mechanism that achieves this.

    GMT is a time zone (since the 1960s).

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