[tz] [PATCH 1/1] Add UTC to zone tables

[J William Piggott]

On 03/10/2016 06:21 PM, Paul Eggert wrote:
> On 03/10/2016 02:04 PM, J William Piggott wrote:
>> Should there be a zone table (tzselect) entry for UTC?
>
> One can use tzselect to choose UTC already, no? Something like the following.

You cannot set /etc/localtime to a posix TZ string.

The Theory file says that tzselect, and applications like it that use
the zone tables, are to assist a layperson it selecting a time zone
_file_ from the database of _files_. IMO, a posix TZ string validator
doesn't even belong in tzselect.

Let me try to express this issue in another way.

The Time Zone Database it made up of binary zone files. If I write the
name of each file on a paper index card and say put these cards in
geographical order in a drawer labeled zone.tab. Where would the UTC card
be?

The consensus seems to be, the UTC index card cannot be placed in the
zone.tab drawer. It must go in a separate drawer all by itself, because
it has no geographic identity.

Civil agreements to use UTC as a 'universal' reference so that globally
connected systems can function efficiently does not nullify the
geographic origin of UTC.

A geographical model with time zones defined as offsets from UTC
requires UTC to have a geographic origin.

https://upload.wikimedia.org/wikipedia/commons/e/e8/Standard_World_Time_Zones.png

The above link is a graphic representation of such a model. Read the text
at the bottom center. Look at the offsets and times along the bottom.
UTC is defined by the prime meridian and it runs smack through London,
because the RGO is UTC's geographic origin.

The zone tables are a text representations of the same model and the
location of UTC is the same. If a user enters the coords +50+00, having
the UTC _file_ presented as one of the _file_ choices is good.

When tzselect is run the first choices are:

Please select a continent, ocean, "coord", or "TZ".
 1) Africa
 2) Americas
 3) Antarctica
 4) Asia
 5) Atlantic Ocean
 6) Australia
 7) Europe
 8) Indian Ocean
 9) Pacific Ocean
10) coord - I want to use geographical coordinates.
11) TZ - I want to specify the time zone using the Posix TZ format.

If you were offered a million dollars to guess which category holds the
UTC _file_, what would you pick? Pacific Ocean? Asia? I think users
searching for UTC know enough about it to associate it with GMT, and
GMT with Greenwich, and Greenwich with London/Britain. Europe would be
the million dollar guess.

Perhaps the issue everyone is having with my patch is the zone table
comment which tzselect would display as:

Please select one of the following time zone regions.
1) Britain (most areas)
2) Britain (Greenwich/GMT/UTC)

Maybe something like this would work:

Please select one of the following time zone regions.
1) Britain
2) UTC - the prime meridian


If not here, then where? Or is your position unchanged that the database
doesn't need a UTC file?