[tz] leap seconds (srsly)

Marshall Eubanks marshall.eubanks at gmail.com
Fri Nov 4 20:43:10 UTC 2011

On Fri, Nov 4, 2011 at 4:02 PM, Steve Allen <sla at ucolick.org> wrote:
> 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.

My prediction is that the above will not happen (assuming the change
goes through) as

- GMT doesn't really exist as a separate time standard
- most people will not notice or care that UTC is drifting off from UT1
- the people doing really precise navigation already use UT1 and have for years

I would be surprised if any lawmaker ever paid any attention to this change.

In order( 2000 years), when we need a leap hour, things may be different.


> 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)
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