[tz] leap seconds (srsly)
sla at ucolick.org
Fri Nov 4 20:02:42 UTC 2011
On Fri 2011-11-04T19:39:04 +0000, Zefram hath writ:
> In a couple of months, a decision is going to be made about possibly
> ceasing leap seconds in UTC. If that happens, the tz database is going
> to be thrown into a world of hurt, as "UTC = GMT" gradually ceases to
> be a viable approximation.
The existing tzcode has most of the complexity needed to handle the
situation using the information in the "leapseconds" file, with
a caveat below about authority.
The bigger problem will lie in trying to infer whether the laws and
practices of some jurisdictions mean that they want "new UTC" (purely
atomic) or "old UTC" (< 1s approximation to GMT). Since the law and
policy makers themselves are generally unaware of the distinction,
this may take some time to sort out. Islamic nations might tend to
choose to stay with earth rotation.
The authority problem lies in whether or not the IERS would interpret
their charter as calling for them to continue to issue leap second
announcments of the sort currently encoded in the "leapseconds" file
for the sake of those countries whose civil time is explicitly based
on GMT as opposed to UTC. In the absence of the single authority
currently in the IERS it could be that multiple authorities would
start pronouncing when their jurisdictions should implement a leap.
That would be a world of hurt.
Steve Allen <sla at ucolick.org> WGS-84 (GPS)
UCO/Lick Observatory--ISB Natural Sciences II, Room 165 Lat +36.99855
1156 High Street Voice: +1 831 459 3046 Lng -122.06015
Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m
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