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    Leap second decision this week?
    From: Frank Reed
    Date: 2022 Nov 15, 06:18 -0800

    Leap seconds are back in the news:

    A few items from the article:

    • A vote, in the form of Resolution D, is expected on Nov. 18 at a meeting in Versailles of the Bureau’s member nations.
    • It should have happened 20 years ago, and if not for political maneuvering, it probably would have happened 20 years ago.
    • Coordinated Universal Time is the world’s official time scale, and will continue to be whether or not it incorporates leap seconds.
    • In effect, a second will vanish. Such an experiment has never been tested on computer systems, and many metrologists fear a digital disaster.
    • The first time in the history of U.T.C. that a negative leap second occurs, and nobody knows what to do.
    • Whatever the outcome of Resolution D, time would retain its ancient link to the stars.
    • 'We know the relationship between atomic time and the rotation of the Earth.' The differences would continue to be calculated and made available, just not actively implemented.

    For celestial navigation, the last item is the key. If leap seconds are dropped, the difference could be accounted for by an annually (or more frequently) published "watch error" that would provide the difference between UTC and Earth rotation time (my brief article on the topic from a decade ago). This difference, of course, is already available and is incorporated into the time-keeping tools of many celestial navigation apps and software tools. Since it is less than one second, it is usually irrelevant to manual celestial navigation equivalent to less than a quarter of a mile in position error at the equator. If leap seconds are formally suspended, that difference will grow over decades. 

    Frank Reed
    Clockwork Mapping / ReedNavigation.com
    Conanicut Island USA

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