Hi Brooks,
Welcome to the list!
On 08/01/14 01:45, Brooks Harris wrote:
On 2014-01-07 03:40 PM, Poul-Henning Kamp wrote:
In message <52cc8c26.5090...@edlmax.com>, Brooks Harris writes:
I fully understand time zone specifications are fractured. My objective
is to determine what standards are most relevant currently, that is,
what standards may be considered "in force". And where none exist, to
state some sort of rules of "common use" or "common practice" without
referring to the impossibly large collection of local jurisdictions and
laws.
There is no way to do that, because timezones are purely a matter
under the jurisdiction of national or in some cases even provincial
governments, and they are free to do any damn thing they want to them.
Yes. What I'm trying to get at is - "Offset from UTC" seems pretty clear
- a given "+-xx:xx" gives you a hard-value to work with in the time
domain. But this doesn't seem to be clearly defined anywhere. I'm
looking for more than "because everybody does it that way".
Meantime, local jurisdictions choose to honor some locally defined "time
zone" including politically defined geographic areas. Time and position
are related but they are not the same. Typically, most elect to follow
"common use" precedent and choose a reasonable even-hour "offset from
UTC". (Yes, I know its sometimes referenced to GMT and other details
like that, and yes, Newfoundland and others are not on the hour.)
Various governments have repeatedly made sure this fact is not
overlooked.
I'm not sure I blame the governments quite so directly. As far as I can
tell both experts and officials are guessing what the "standards" of
"timezone" might be, so how can they be expected to conform to a
non-existent ideal? If someone is in charge of deciding the rules and
parameters of some time zone somewhere, what guidence do they have? And
the more you research it, the more confusing it becomes.
I think they mostly adapt to what is handy for trade. Keeping the same
clock as important neighbors to which they have lots of trade and
communication, that is in practice more important that aligning to the
15 degrees separations, even if that is a starting-point. The same goes
for the daylight-saving time. In Europe, the European Union coordinated
the daylight-saving time transitions to be at the same time amongs
members, as this avoids switching at different dates. This however is
not coordinated with the US, so I can have 8, 9 and 10 hours between me
and California for example. It's also interesting to note that this
common document from 2001 have different types of formulations depending
on language, so GMT, meridian and UTC is used alternatively depening on
language, and if you want to be picky, you don't know relative time
between countries better than +/- 0.9 s.
So, it's a mess. It's not a technical problem, it just becomes one.
A) "International Date Line", which is probably not standardized
[...]
It is not.
In only exists as a the result of local governments deciding what
timezones to use.
Some Pacific Island nation "jumped" timezones for Y2K in order
to be the first country to "arrive in the new millenia.
The "intenational date line" is simply where you, in broad daylight,
have a country with one date on one side and another country with
a different date on the other side.
Yes. But its "roughly" 180 degrees from the "Greenwich meridian", as per
"International Meridian Conference of 1884" "Final Act III. "That from
this meridian longitude shall be counted in two directions up to 180
degrees, east longitude being plus and west longitude minus."
Its common practice that the jump to the designation of the next day
occurs at this "international date line", wherever the local authorities
may have chosen to place themselves, for examples UTC-offset +14:00,
+13:00, and +12:00. This topic, of jumping to the next day, is discussed
in many letters and common explanations, but I find no official
statement to that effect, even as a guideline.
B) The "International Meridian Conference of 1884" contains significant
discussion of the idea "That these standard meridians should continue to
be designated as even multiples of fifteen degrees from Greenwich", but
there appears to be no explicit resolution of vote on the topic.
And there were none subsequently. Strict 15 degree meridians would
be very impractical, unless national borders were aligned with them.
Well, thats what even-hour UTC-offsets are, aren't they? And in
jurisdictions with even-hour UTC offsets, that's where they've placed
themselves in the timescale, right?
Despite significant attempts at map-redrawing in the first half of
the 19-hundredes, timezones were never a reason for it.
UTC was standardized so that telephone, telegraph and radio operators
would not have to keep track of local politics all over the world in
order to operate.
Right. And it almost works. It seems to me it could work better if the
loose ends of the underlying standards were better taken care of, hence
my interest in learning the current state of the definition of each of
these components.
In practice, the "olsen" database is a post-facto recording of
political whims with respect to timezones.
Again, "political whims" is really all they've got to go on. Maybe we
can do better?
Not without a lot of political whims. Simply put, just forget it, won't
happen.
It might improve, but the end game is way to far away.
Cheers,
Magnus
_______________________________________________
LEAPSECS mailing list
LEAPSECS@leapsecond.com
http://six.pairlist.net/mailman/listinfo/leapsecs
