Re: Leap Seconds

[Wilhelm.Spickermann@t-online.de (Wilhelm Spickermann)]

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On 31-May-01 Marin David Condic wrote:
> O.K. See my other post above - I phrased my original statement badly. You
> are right that a measure of absolute seconds is going to remain constant. I
> was thinking with respect to computing those seconds relative to dates. We
> agree on a date/time to meet. You compute the seconds between now and then
> and I compute the seconds between now and then and we both delay N seconds.

Hmm, none of us can compute the number of seconds before the IERS has
determined all the leap seconds in that time range. Once the leap seconds or
their absence are determined, we will get the same results.

> Your computation involves leap-seconds and mine doesn't. We've got a problem
> in that one of us will be there early.
> 
But a look on the next wall clock will show, who computed the wrong result (we
agreed upon a specific date and time). None of us will be early, if we interpret
the results of the computation correctly. 

The computation which includes leap seconds will compute the time difference and
the result can be used in a simple countdown clock or (hopefully) a delay
statement. The computation has to be postponed until the necessary information
is available.

The computation without leap seconds can be done at once but it doesn�t compute
a time difference. But the result can be compared to a POSIX clock, as this type
of "clock" jumps with every leap second inserted or omitted. The result is
unusable for delay statements. (I hope at least no one wants "delay 1.0;" to
mean "don�t wait" if its execution happens to fall on a negative leap second.)

Wilhelm