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    Re: NIST website time accuracy
    From: Paul Hirose
    Date: 2010 Aug 19, 11:20 -0700

    Gary LaPook wrote:
    > I now have three clocks running on my computer, NIST (
    > http://nist.time.gov/timezone.cgi?Pacific/d/-8/java# ), Navy celnav
    > website (
    > http://www.usno.navy.mil/USNO/astronomical-applications/data-services/cel-nav-data
    > ) and the USNO time website that you pointed out (
    > http://www.usno.navy.mil/USNO/time/display-clocks/simpletime )
    I checked them against WWV on a shortwave radio.
    #1 was consistently a little slow, perhaps .1 second. The claimed
    accuracy on the Web page was 1 second or .5 second (I tested it four
    times). It seemed that the error would vary during the course of a
    single minute, but WWV was fading in and out so I couldn't be sure. At
    the top of each minute the error was consistent.
    #2 is the one I have the most experience with. Over the past couple
    years or so I've tested it several times against WWV and it has always
    been perfect as far as my ear and eye could judge. The only exception
    was one time when I loaded the page while a file download ran in the
    background, just to see if there would be an effect. The clock was off
    by a split second in that case.
    #3 was perfect. I tested it three times over the course of a few minutes.
    I loaded only one of these pages at a time, and kept the page displayed
    just long enough to catch the WWV beep at the top of the minute.
    I filter out messages with attachments or HTML.

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