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Leap Second At The End of 2005

Posted by CmdrTaco on from the correct-your-watches-immediately dept.

Ruff_ilb writes "Because of the discrepency between an ephemeris second (the fraction 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time) and the second of atomic time (the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom), we're left with more than leap years. In order to ensure that the the atomic time and civil stay coordinated, "Civil time is occasionally adjusted by one second increments to ensure that the difference between a uniform time scale defined by atomic clocks does not differ from the Earth's rotational time by more than 0.9 seconds."" And Happy New Years everyone ;)

5 of 269 comments (clear)

  1. Re:How did you use yours? by tonsofpcs · · Score: 4, Informative

    Most NTP servers use UTC time, so yes.

    http://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat - leap second bulletin

    --
    Video Production Support
  2. Highlights problem with ntp... by Dr.+Zowie · · Score: 4, Informative
    The NTP protocol that all of us cool kids use to synchronize our computers' clocks has a fundamental flaw -- the NTP time is tied to UTC, but contains no leap seconds at all, more like TAI, the atomic time standard. When there's a leap second, the system's solution is to ignore it.

    So, as of today, any time stamp you have made using NTP, ever, has been retroactively displaced by one second. Intervals that included midnight (UTC) last night are all too short by one second.

    This may not be a problem for handling your calendar appointments, but it can muck up all kinds of scientific applications that require high precision.

  3. time.gov by srblackbird · · Score: 5, Informative

    I watched the time at Time.gov: 23:59:56 (UTC) =>23:59:57=>23:59:58=>23:59:59=>23:59:60!=>00:00:0 0
    It was Amazing! This was the first time for me... *remebers where I was at that moment

    --
    "The test of the morality of a society is what it does for it's children." -Dietrich Bonhoeffer
    1. Re:time.gov by Rytsarsky · · Score: 4, Informative

      Screenshot: http://flickr.com/photos/jk3us/79978824/

      --
      God became man to enable men to become sons of God. -C.S. Lewis
  4. It's not the 'ephemeris second' that's the problem by Jonathan+McDowell · · Score: 5, Informative

    Original poster is slightly wrong - it's not the length of the 1900 ephemeris second,
    it's the fact that the Earth, like all of us, is getting older and slowing down, so that
    the 2005 "Earth rotation" second (i.e. 1/86400 of one spin of the Earth) is longer than
    the 1900 equivalent and longer than the atomic time (SI) second. Instead of changing
    the length of the second, it is currently deemed less painful to keep using the old
    length and stick in an extra second every now and again.

    Since this depends on the slop of the Earth's interior, it's not a fully regular and predictable thing - we might even have to remove a second one year.