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    Re: Definition of the twilight intervals
    From: Gary LaPook
    Date: 2015 Aug 17, 15:54 -0700

    FWIW, Federal Aviation Regulation 1.1 defines:

    "Night means the time between the end of evening civil twilight and the beginning of morning civil twilight, as published in the Air Almanac, converted to local time."

    Symantically, this indicates that civil twilight is a period of time, not a particular instant. If it were a particular instant then the defination would read:

    "Night means the time between evening civil twilight and  morning civil twilight, as published in the Air Almanac, converted to local time"

     

    See:

    14 CFR 1.1

    gl

    .

       
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