Leap second tonight

Peter Beckman beckman at angryox.com
Mon Jan 5 21:19:28 UTC 2009

I've gleened from this thread that:

     * everyone uses UTC, or should, because UTC is a uniform time scale,
       except for those leap seconds
     * UTC is sourced from the frequence of a radio emission from cesium
       atoms which are extremely constant
     * UTC can get out of whack with the rotation of the earth around the
       sun, because our rotation is not uniform, but is calculated rather
       than measured (well, sort of)
     * UTC is TAI plus leap seconds.  In 1972, when leap seconds were first
       introduced, UTC was TAI - 10 seconds.  UTC is now TAI - 34 seconds.
       TAI ticks exactly as fast as UTC, ignoring leap second adjustments.
     * UTC is slower than UT1 by about 1ms per day.
     * On 12/31/2008 UTC was (-) 591.8ms behind UT1.  On 1/1/2008 UTC was
       407.1ms ahead of UT1.
     * Leap seconds are applied to UTC every few years to remain in line
       with UT1, the time based on the rotation of the earth around the sun.
     * GMT is used to imply UT1, but sometimes UTC, but really GMT is just
       massively confusing and you shouldn't use it, either in conversation
       or in your servers/routers, because nobody is really sure without
       reading a lot of documentation what GMT means for each
     * When writing code regarding dates and times, know that any year may
       have 366 days, and any minute may have 61 seconds.
     * When in doubt, Dr.  Daniel Gambis is always right.


On Mon, 5 Jan 2009, Marshall Eubanks wrote:

> Having been involved in the leap second business, I can tell you that
> Daniel Gambis strictly follows the rules, which are Bulletin C is mailed
> every six months, either to announce a time step in UTC or to confirm
> that there will be no time step at the next possible date.

Peter Beckman                                                  Internet Guy
beckman at angryox.com                                 http://www.angryox.com/

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