TAI zone?

Clive D.W. Feather clive at davros.org
Fri Jul 1 12:37:55 UTC 2011

Russ Allbery said:
>>> The alternative proposal is that leap seconds be declared twenty years
>>> in advance ...
>> Is that actually possible?
> Well, sure, provided that we're okay with twenty years of drift.  It
> increases the divergence between UTC and the physical phenomenon that it's
> intended to mirror, of course, but it bounds that divergence at about
> thirty or forty years worth of divergence (assuming that we'll continue to
> use the current low rate of changes) instead of six to twelve months of
> divergence.  Given the low rate of divergence currently, this doesn't seem
> like a big deal.  Having noon be 20 seconds, or even a minute, off true
> value doesn't seem like it would be too horrible.  Or at least the article
> in ACM was fairly convincing.

The first problem is that there's various things around which assume that
the divergence will remain under a second. Nobody knows how many of them
will break and how important that is.

The second, longer-term problem is that the rate we need leap seconds is
increasing quadratically. That makes keeping within that 1 second bound
ever harder to predict.

Clive D.W. Feather          | If you lie to the compiler,
Email: clive at davros.org     | it will get its revenge.
Web: http://www.davros.org  |   - Henry Spencer
Mobile: +44 7973 377646

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