[H-GEN] time in C/C++

[David Starkoff]

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On Wed, Dec 29, 1999 at 05:02:04PM +1000, Paul Gearon wrote:

> Well I can't comment on leap-seconds (as I don't know when they
> occur), [...]

Some general information on leap seconds is at:

  http://tycho.usno.navy.mil/leapsec.html

(Or, if that's too much to type, just use ``leap second'' in Google and
hit ``I'm feeling lucky''.  Google is wonderful.  Google rocks my
world.)

There appears to be no more than six months notice of a upcoming leap
second, which is to ensure that the difference between the time measured
by the rotation of the Earth and UTC is always less than 0.9 s; with
preference given to the end of June or December, then to the end of
March or September.

The URL above tells us:

  Through the use of ancient observations of eclipses, it is possible to
  determine the average deceleration of the Earth to be roughly 1.4
  milliseconds per day per century.

And, that:

  Over the course of one year, the difference accumulates to almost one
  second, which is compensated by the insertion of a leap second into
  the scale of UTC with a current regularity of a little less than once
  per year.

A list of previous leap seconds is at:

  ftp://maia.usno.navy.mil/ser7/tai-utc.dat

As leap seconds were introduced in 1972, and there have only been 22 of
them, barring a cosmic calamity sufficient to grossly retard (or
accelerate --- leap seconds can go in both directions), I would have
thought that for financial purposes, they could be safely ignored for
the next few millenia.

David.
-- 
``I have always endeavoured to be cognitive in all my cognitive endeavours.''

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