[tz] Preparing to fork tzdb
brooks at edlmax.com
Wed Sep 22 18:32:01 UTC 2021
On 2021-09-22 9:17 AM, Eliot Lear via tz wrote:
> On 22.09.21 15:09, dpatte via tz wrote:
>> Iso is a living international standard, and it's their mandate, not
>> the mandate of timezone collectors to do the negotiation and
>> diplomacy in order to arrive at and maintain the world standard.
> Right. And this group has avoided their business for decades.
I agree. There should be only one 'authority' for country codes, and ISO
3166 is it as far as I know.
It seems it is the mapping of the country codes to time zone names
(tags) that is causing the current difficulties. It seems to me it
should not be such a problem. As zone1970.tab (and zone.tab) says:
# This table is intended as an aid for users, to help them select timezones
# appropriate for their practical needs. It is not intended to take or
# endorse any position on legal or territorial claims.
It is useful for "practical needs" but cannot be relied upon in all
circumstances. Tzdb can use ISO 3166 but should not alter it or fall
victim to any political controversies it might imply.
I would point out, however, that zone1970.tab also contains the time
zone *coordinates*. This is different matter than country codes. In the
work I'm doing the coordinates are important. They define the
approximate default coordinates of time zones, and this is useful in a
number of ways, indicating geographic distances between time zones and
distinction of Northern and Southern hemispheres.
I think this has significance to the 'merging' controversy.
"Europe/Oslo" is not the same time zone as "Europe/Berlin". They may
have been using the same rule sets since 1970 resulting in identical
local YMDhms representations but they have different time zone names
(tags) and distinct coordinates. Oslo is not the same city as Berlin. If
time zone "Europe/Oslo" ever existed it still exists today.
"Europe/Oslo" could adopt a new set of rules different from
"Europe/Berlin" and its possible they might given the new elective rules
being suggested by the EU.
Olsen's original insight to use towns and cities to name time zones
turns out to be extraordinarily useful. Whether or not "Europe/Oslo" is
in Norway is entirely beside the point of local time in the
"Europe/Oslo" time zone. Time zones really exist only in the time domain
relative to the (special) "Etc/UTC" time zone. I'm sure most
contributors to the tz list understand this, but there's a natural
tendency equate a time zone with a location or place since this is where
the general idea comes from to begin with. But I think tzdb must be
vigilant to maintain this conceptual separation of time zone v.s.
"place", especially in regard to politically named and claimed
geographic boundaries such as Norway or Germany.
This separation of "time" from "place" may seem inconsistent with my
previous point about time zone coordinates but I don't think so. The
time zone names are based on cities and the cities have approximate
geographical location and this ties the time zone to a location. This is
useful for some important purposes and supports the basic idea behind
time zones. But it is a separate conceptual and implementation
consideration from the local time zone YMDhms representation with
respect to "Etc/UTC". The geographic coordinates have nothing to do with
the local time because any time zone may adopt any UTC-offset (STDOFF)
or DST rules they choose and this decouples the time zone's local time
from the city location.
I'm sure most tzdb experts recognize this distinction but it seems to
have somehow been lost track of recently. I hope participants can find
the way back to the cooperation that has characterized the group for so
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