On Thu 2003-07-03T15:13:55 +0100, Ed Davies hath writ:
> Markus Kuhn wrote:
> > ... because it
> > seems inconvenient as long as politicians worldwide can't agree on
> > common dates of switching between summer and winter time. ...
>
> Well, would you vote for a politician who would agree to ending
> summer time on the same day over thw whole world - both northern
> and southern hemispheres?
Which is exactly why I chose Jan 1 0h TI as the time of the change in
DUTH. It was intended not to be the summer time change date for
anyone. Any other moment works fine, perhaps even the Jan 1 Greenwich
noon which J. Levine has noted is the closest thing to a world
holiday moment.
> More seriously, I'm not sure why a common date is required.
Right. To be more explicit:
For places which observe summer time, the DUTH offset from UTH is
consulted only at the moment when summer time is to begin. If DUTH
incremented last January, then the legislated summer time zone offset
will already be in effect, and the summer time zone increment will be
omitted that year. So places in the N hemisphere will omit the usual
summer increment to their zone times sometime around April, and places
in the S hemisphere will omit the usual summer increment sometime
around October.
For places where summer time is not observed, the DUTH increment can
be applied at any time deemed convenient by their legislature. Of
course they'll hate this plan the most, for their choice to avoid
summer time was presumably intended to avoid ever having their zone
time change by an hour.
The point being that the changes in DUTH are required to be predicted
at least 10 years in advance. Indeed, upon thinking it seems that
rule could be even more conservative. It could start off being 100
years of advance notice and stay that way more than long enough for
the next round of ITU discussions to be organized, convene, declare
that the DUTH scheme is poppycock, and come up with a replacement more
conducive to the software systems of their era.
A bad problem with the DUTH scheme is that it will not be tested for
over 500 years, so it is still forcing a Y2K-like global systems
review onto posterity.
This is not to say that I want to see the demise of UTC with leap
seconds. I find that the 1000+ year interval over which the current
scheme will work is more than long enough to justify doing nothing
now.
--
Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064
sla_at_ucolick.org Voice: +1 831 459 3046 http://www.ucolick.org/~sla
PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E 49 89 0E FE 26 B4 14 93
Received on Thu Jul 03 2003 - 08:44:04 PDT