Theory - zone name, zone creation, zone lifetime

[Mr tobias conradi]

>>Theory reads:
>>To represent this data, the world is partitioned 
>>into regions whose clocks all agree
>>
>> 1) Where are these regions listed?
>> The only lists of geographical areas I could find are:
>> - the zones in zone.tab
>> - (current) countries in iso3166.tab

>Yes, that's where the regions are listed in the database.
>There are efforts to list the boundaries of the regions,
>but these are outside the scope of the current database.
Since iso3166.tab contains geographic areas whose clocks
did not all agree, the place seems to be zone.tab.

Zone.tab speaks of "zone" not of "region".

Ammendement to Theory:
To represent this data, the world is partitioned 
into regions <NEW>, named time zone,</NEW> 
whose clocks all agree

OR

To represent this data, the world is partitioned 
into regions <NEW>, named time zone and listed in zone.tab,</NEW> 
whose clocks all agree

>> Theory reads:

>> Use ISO 3166 (see the file iso3166.tab) to help
>> decide whether something is a country.
>> [...]
>> or when locations change countries
>> (e.g. Hong Kong from UK colony to China)
>> 
>> Issue:
>> 1) "help to decide" - decision process is undefined.

>It is not a deterministic algorithm; there are border cases
>that require human judgment.

Any example?


>> 2) Hong Kong is listed in iso3166.tab as HK.
>> For the purpose of zone creation is it
>> 2a) a country,

>Yes, that's right.

Ammendement to Theory:
OLD
or when locations change countries
(e.g. Hong Kong from UK colony to China)

NEW
or when locations change countries
(e.g. Hong Kong from UK to China)

Reason: "UK colony" is not a country. Use same 
level as for "China".

>> Theory reads:

>> E.g. prefer `Paris' to `France', since
>> France has had multiple time zones.
>> 
>> Issue:
>> 1) It does not matter what zones France "had" in the past.
>> 2) It may matter that Europe/Paris might be split in the future.

>Yes, (2) is the point.


>> 3) There is no proof in zone.tab that France had
>> multiple time zones at all

>It did, during both World War I and World War II.  
>Shanks & Pottenger partition France 
>into 28 distinct regions.  But this sort of detail
>isn't needed in the table.

Thanks. Since WWI and WWII took place before 1970, 
that does not matter for tzdata purpose. 

Ammendement to Theory:
OLD
E.g. prefer `Paris' to `France', since 
France has had multiple time zones.

NEW
E.g. prefer `Paris' to `France', since 
France may be split into multiple time zones
in the future.

Reason:
Refer to a fact that matters (2) instead of 
one that does not matter (3).

 
--
Tobias Conradi
Rheinsberger Str. 18
10115 Berlin, Germany