[fitsbits] communique from the leap second wars

[seaman at hanksville.org]

Summary:  We should make plans now about how FITS would support UTC
should the issuance of leap seconds be halted.

Straw proposal:  Replace all instances of "UTC" with "UT1" in the FITS
standard.  Begin working on a more extensive proposal for generalized
time handling in keywords and tables.

Discussion:  For the past five years (beginning before Y2K), a group of
representatives of the precision timing community have been attempting
to halt the issuance of leap seconds.  The effect of this would be to
completely disconnect civil time, which would remain UTC in name only,
from the rotation of the Earth.  I won't belabor the implications of
this except to note that a wide range of astronomical software and
systems would have to be rewritten simply to preserve current
functionality, just as with Y2K.  The latest attempt is to cast this as
a replacement of leap seconds issued roughly every 18 months, by leap
hours issued roughly every 600 years (the effect is quadratic).  One
has a hard time imagining how such a standard would be enforced -
Universal Time would simply cease to exist as we know it.

I've appended the retroactive announcement that such a vote occurred
(and the implication that they'll try again next year).  If you think
the IAU governs this decision, think again.  There is no indication
that the draft standard will ever be released for comment to the (many)
interested parties, but a bootleg version is available from
http://www.fcc.gov/ib/sand/irb/weritacrnc/archives/nc1893wp7a/1.doc.

Steve Allen of Lick Observatory provides an excellent web resource on
the issues:

http://www.ucolick.org/~sla/leapsecs

My own take on the subject is available from:
http://iraf.noao.edu/~seaman/leap

Rob Seaman
National Optical Astronomy Observatory
---

> From:     matsakis.demetrios at USNO.NAVY.MIL
Subject:  [LEAPSECS] ITU Meeting last year
Date:     January 19, 2005 1:19:42 PM MST
To:       LEAPSECS at ROM.USNO.NAVY.MIL

This is a very brief description of what happened at last October's ITU
meeting in Geneva.

A resolution was proposed to redefine UTC by replacing leap seconds by
leap hours, effective at a specific date which I believe was something
like 2020.

This proposal was not passed, but remains under active consideration.
Presumably something like it will be considered next year.  My quick
computation indicates that, should this proposal be adopted, it would
take about a century for UT1-UTC to diverge by one minute, and many
centuries before a leap-hour would be called for.

I did not attend the meeting, and this is all I know.  I was told the
ITU web pages had essentially this same information in them, but could
not find anything there with their search engine.